Post-effective amendment to a registration statement that is not immediately effective upon filing

STOCK-BASED COMPENSATION Stock Option Activity (Detail)

v2.4.1.9
STOCK-BASED COMPENSATION Stock Option Activity (Detail) (USD $)
6 Months Ended 12 Months Ended
Mar. 31, 2015
Sep. 30, 2014
Option Shares Outstanding    
Outstanding, Beginning Balance 8,637,962us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Awarded 2,987,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross  
Exercised 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Forfeited 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod  
Outstanding, Ending Balance 11,625,462us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Vested 7,399,875us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares  
Vested and expected to vest 11,625,492us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber  
Weighted Average Exercise Price    
Outstanding, Beginning Balance $ 0.38us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Awarded $ 0.19us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice  
Exercised $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice  
Outstanding, Ending Balance $ 0.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Vested $ 0.32arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice  
Vested and expected to vest $ 0.31us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice  
Weighted Average Remaining Contractual Term (years)    
Awarded 0 years  
Exercised 0 years  
Forfeited 0 years  
Balance 5 years 4 months 28 days  
Vested 4 years 10 months 2 days  
Vested and expected to vest 5 years 4 months 28 days  
Aggregate Intrinsic Value    
Outstanding, Beginning Balance $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Awarded 0arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAwardedAggregateIntrinsicValue  
Exercised 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue  
Forfeited 0arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodAggregateIntrinsicValue  
Outstanding, Ending Balance 7,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Vested 5,243arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriodAggregateIntrinsicValue  
Vested and expected to vest 7,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue  
Employee Stock Option [Member]    
Option Shares Outstanding    
Outstanding, Beginning Balance   3,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Awarded   5,869,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercised   (231,250)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Forfeited   0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Outstanding, Ending Balance   8,637,962us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested   4,645,935us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested and expected to vest   8,637,962us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Weighted Average Exercise Price    
Outstanding, Beginning Balance   $ 0.38us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Awarded   $ 0.33us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercised   $ 0.40us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Outstanding, Ending Balance   $ 0.34us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested   $ 0.36arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested and expected to vest   $ 0.34us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Weighted Average Remaining Contractual Term (years)    
Awarded   0 years
Exercised   0 years
Forfeited   0 years
Balance   5 years 5 months 16 days
Vested   4 years 7 months 6 days
Vested and expected to vest   5 years 5 months 16 days
Aggregate Intrinsic Value    
Outstanding, Beginning Balance   0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Awarded   0arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAwardedAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercised   0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Forfeited   0arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeitedInPeriodAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Outstanding, Ending Balance   2,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested   76arth_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedInPeriodAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Vested and expected to vest   $ 2,750us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember