Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details)

v2.4.1.9
Stockholders' Equity (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Class of Stock [Line Items]      
Common Stock, Capital Shares Reserved for Future Issuance 16,431,666us-gaap_CommonStockCapitalSharesReservedForFutureIssuance    
Stock Repurchased and Retired During Period, Shares 10,900,000us-gaap_StockRepurchasedAndRetiredDuringPeriodShares 11,500,000us-gaap_StockRepurchasedAndRetiredDuringPeriodShares  
Repurchases of common stock $ 328,300,000us-gaap_PaymentsForRepurchaseOfCommonStock $ 289,900,000us-gaap_PaymentsForRepurchaseOfCommonStock $ 0us-gaap_PaymentsForRepurchaseOfCommonStock
Stock Repurchase Program, Remaining Authorized Repurchase Amount 182,200,000us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1    
Stock Repurchase Program, Authorized Amount $ 800,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1    
Common Class A      
Class of Stock [Line Items]      
Common Stock, Shares Authorized 2,000,000,000us-gaap_CommonStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		2,000,000,000us-gaap_CommonStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember 		 
Common Class C      
Class of Stock [Line Items]      
Common Stock, Shares Authorized 2,000,000,000.0us-gaap_CommonStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassCMember