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Stockholders' Equity (Details) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified
3 Months Ended
Mar. 27, 2015
Mar. 28, 2014
Stockholders' Equity Note [Abstract]    
Stock Repurchase Program, Number of Shares Authorized to be Repurchased 233.0us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased  
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased 16.0us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased  
Stock Repurchased and Retired, Share, Total 217.0altr_StockRepurchasedandRetiredShareTotal  
Payment For Stock Repurchased and Retired, Total $ 5,000,000,000altr_PaymentForStockRepurchasedandRetiredTotal  
Stock Repurchased and Retired During Period, Shares 1.6us-gaap_StockRepurchasedAndRetiredDuringPeriodShares 4.6us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Payments for Repurchase of Common Stock $ 57,507,000us-gaap_PaymentsForRepurchaseOfCommonStock $ 161,794,000us-gaap_PaymentsForRepurchaseOfCommonStock
Common Stock Repurchased and Retired During The Period, Average Cost Per Share $ 34.95altr_CommonStockRepurchasedandRetiredDuringThePeriodCostPerShare $ 35.16altr_CommonStockRepurchasedandRetiredDuringThePeriodCostPerShare