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Common Stock (Narrative) (Detail) (USD $)
0 Months Ended
Feb. 05, 2015
Dec. 04, 2014
Sep. 04, 2014
May 07, 2015
May 08, 2014
Dividends Payable [Line Items]          
Common Stock, Dividends, Per Share, Declared $ 0.06us-gaap_CommonStockDividendsPerShareDeclared $ 0.06us-gaap_CommonStockDividendsPerShareDeclared $ 0.06us-gaap_CommonStockDividendsPerShareDeclared    
Dividends declared, date of declaration Feb. 05, 2015 Dec. 04, 2014 Sep. 04, 2014    
Dividends declared, date of distribution Mar. 26, 2015 Dec. 29, 2014 Sep. 29, 2014    
Dividends declared, date of record Mar. 12, 2015 Dec. 15, 2014 Sep. 15, 2014    
Stock repurchase program          
Dividends Payable [Line Items]          
Number of shares authorized to be repurchased         5,000us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
/ us-gaap_ShareRepurchaseProgramAxis
= acet_ShareRepurchaseProgramMember
Subsequent Event          
Dividends Payable [Line Items]          
Common Stock, Dividends, Per Share, Declared       $ 0.06us-gaap_CommonStockDividendsPerShareDeclared
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
 
Dividends declared, date of declaration       May 07, 2015  
Dividends declared, date of distribution       Jun. 25, 2015  
Dividends declared, date of record       Jun. 11, 2015