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

Subsequent Events - Additional Information (Detail)

v2.4.1.9
Subsequent Events - Additional Information (Detail) (USD $)
1 Months Ended 12 Months Ended
Jan. 30, 2014
Sep. 30, 2014
Dec. 31, 2014
Sep. 30, 2013
Dec. 01, 2014
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share   $ 0.001us-gaap_CommonStockParOrStatedValuePerShare $ 0.001us-gaap_CommonStockParOrStatedValuePerShare $ 0.001us-gaap_CommonStockParOrStatedValuePerShare  
Common stock, shares, outstanding   72,076,487us-gaap_CommonStockSharesOutstanding 76,076,487us-gaap_CommonStockSharesOutstanding 60,145,237us-gaap_CommonStockSharesOutstanding  
Private Placement          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share   $ 0.001us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
$ 0.001us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
   
Common stock, shares, outstanding   76,076,487us-gaap_CommonStockSharesOutstanding
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
     
Proceeds from Issuance of Common Stock $ 2,850,000us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
$ 800,000us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
     
Series B Warrants | Private Placement          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock aggregate issuance   4,000,000arth_CommonStockAggregateIssuance
/ us-gaap_StatementClassOfStockAxis
= arth_SeriesBWarrantsMember
/ us-gaap_SubsidiarySaleOfStockAxis
= us-gaap_PrivatePlacementMember
     
Series B Warrants | Subsequent Event | Minimum          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share         $ 0.20us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_StatementClassOfStockAxis
= arth_SeriesBWarrantsMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Series B Warrants | Subsequent Event | Maximum          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share         $ 0.35us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_StatementClassOfStockAxis
= arth_SeriesBWarrantsMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Series C Warrants | Subsequent Event | Minimum          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share         $ 0.20us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_StatementClassOfStockAxis
= arth_SeriesCWarrantsMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Series C Warrants | Subsequent Event | Maximum          
Business Acquisition, Equity Interests Issued Or Issuable [Line Items]          
Common stock, par or stated value per share         $ 0.40us-gaap_CommonStockParOrStatedValuePerShare
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_StatementClassOfStockAxis
= arth_SeriesCWarrantsMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember