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STOCK-BASED COMPENSATION - Additional Information (Detail) (USD $)
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3 Months Ended |
12 Months Ended |
1 Months Ended |
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Dec. 31, 2014
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Dec. 31, 2013
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Sep. 30, 2014
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Sep. 30, 2013
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Oct. 02, 2014
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Oct. 31, 2013
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Jun. 18, 2013
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Oct. 02, 2013
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Sep. 30, 2009
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| common stock, shares, issued |
76,076,487us-gaap_CommonStockSharesIssued
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72,076,487us-gaap_CommonStockSharesIssued
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60,145,237us-gaap_CommonStockSharesIssued
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| Increase In Aggregate Number Of Shares |
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3,000,000arth_IncreaseInAggregateNumberOfShares
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| Percentage of outstanding number of shares |
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4.00%arth_PercentageOfOutstandingNumberOfShares
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| Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average remaining contractual term |
5 years 5 months 8 days
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5 years 5 months 16 days
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| Share-based compensation arrangements by share-based payment award, options, grants in period, weighted average exercise price |
$ 0.17us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
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$ 0.33us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, expected volatility rate, minimum |
77.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
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77.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, expected volatility rate, maximum |
119.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
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134.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, risk free interest rate, minimum |
0.25%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
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0.83%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, risk free interest rate, maximum |
2.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
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2.52%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
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| Share based compensation arrangement by share based payment award fair value assumptions expected forfeiture rate |
0.00%arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedForfeitureRate
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0.00%arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedForfeitureRate
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, expected dividend rate |
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
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0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
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| Share-based compensation arrangement by share-based payment award, number of shares available for grant |
3,707,544us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
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1,361,985us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
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| Allocated share-based compensation expense |
$ 278,000us-gaap_AllocatedShareBasedCompensationExpense
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$ 132,000us-gaap_AllocatedShareBasedCompensationExpense
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$ 1,101,000us-gaap_AllocatedShareBasedCompensationExpense
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$ 288,000us-gaap_AllocatedShareBasedCompensationExpense
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| Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition |
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2 years 11 days
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| Common Stock, Shares Authorized |
300,000,000us-gaap_CommonStockSharesAuthorized
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300,000,000us-gaap_CommonStockSharesAuthorized
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300,000,000us-gaap_CommonStockSharesAuthorized
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| Restricted Stock or Unit Expense |
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95,000us-gaap_RestrictedStockExpense
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0us-gaap_RestrictedStockExpense
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |
537,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
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5,869,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
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| Research and Development Expense |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Allocated share-based compensation expense |
121,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
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86,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
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629,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
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38,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_ResearchAndDevelopmentExpenseMember
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| General and Administrative Expense |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Allocated share-based compensation expense |
157,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember
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46,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember
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472,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember
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250,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember
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| Maximum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, expected term |
10 years
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10 years
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| Minimum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, fair value assumptions, expected term |
9 months 18 days
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2 years 4 months 24 days
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| Employees And Directors |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |
4,102,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesAndDirectorsMember
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| Consultants |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Stock Issued During Period, Shares, New Issues |
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3,565,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_TitleOfIndividualAxis
= arth_ConsultantsMember
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |
5,304,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_TitleOfIndividualAxis
= arth_ConsultantsMember
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2,465,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_TitleOfIndividualAxis
= arth_ConsultantsMember
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| Employees |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Stock Issued During Period, Shares, New Issues |
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5,304,212us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross |
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3,404,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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| Employees | Maximum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangements by share-based payment award, options, grants in period, weighted average exercise price |
$ 0.22us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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$ 0.37us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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| Employees | Minimum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangements by share-based payment award, options, grants in period, weighted average exercise price |
$ 0.17us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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$ 0.17us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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| 2013 Stock Incentive Plan |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| common stock, shares, issued |
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7,825,388us-gaap_CommonStockSharesIssued
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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| Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, total |
$ 801,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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$ 965,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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| Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition |
1 year 9 months 25 days
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| Common Stock, Shares Authorized |
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13,114,256us-gaap_CommonStockSharesAuthorized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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10,231,197us-gaap_CommonStockSharesAuthorized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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10,231,197us-gaap_CommonStockSharesAuthorized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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| Share-based compensation arrangement by share-based payment award, number of additional shares authorized |
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2,883,059us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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2,405,809us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndThirteenStockIncentivePlanMember
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| 2013 Stock Incentive Plan | Consultants |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, award vesting period |
4 years
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| 2013 Stock Incentive Plan | Consultants | Maximum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average remaining contractual term |
10 years
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10 years
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| Share-based compensation arrangement by share-based payment award, award vesting period |
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3 years
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| 2013 Stock Incentive Plan | Consultants | Minimum |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Share-based compensation arrangement by share-based payment award, options, outstanding, weighted average remaining contractual term |
1 year
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3 years
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| Share-based compensation arrangement by share-based payment award, award vesting period |
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1 year
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| 2009 Stock Incentive Plan |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| common stock, shares, issued |
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707,460us-gaap_CommonStockSharesIssued
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndNineStockIncentivePlanMember
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| 2009 Stock Incentive Plan | Consultants |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Additional Common Stock Shares Subject To Vesting Issued |
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116,973arth_AdditionalCommonStockSharesSubjectToVestingIssued
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndNineStockIncentivePlanMember
/ us-gaap_TitleOfIndividualAxis
= arth_ConsultantsMember
|
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| 2009 Stock Incentive Plan | Employees |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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| Common Stock Shares Subject To Vesting Issued |
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579,026arth_CommonStockSharesSubjectToVestingIssued
/ us-gaap_PlanNameAxis
= arth_TwoThousandAndNineStockIncentivePlanMember
/ us-gaap_TitleOfIndividualAxis
= arth_EmployeesMember
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