Repurchases of Outstanding Securities (Details) (USD $)	3 Months Ended				9 Months Ended	12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Accelerated Stock Buyback (Details) [Abstract]
Accelerated stock buyback, gross price paid			$ 200,000,000
Accelerated stock buyback, initial shares delivered (shares)			4,592,423
Accelerated stock buyback, value of initial shares delivered			160,000,000
Accelerated stock buyback, additional shares delivered at settlement (shares)	816,916
Accelerated stock buyback, value of final settlement	40,000,000
Repurchases of Outstanding Securities (Details) [Abstract]
Authorized aggregate amount					1,250,000,000
Total number of shares repurchased since inception of our stock repurchase program (shares)					36,177,737	31,120,279
Aggregate purchase price of shares repurchased since inception of our stock repurchase program					994,800,000	777,300,000
Number of shares repurchased (shares)		0		465,035
Purchase price of shares repurchased				$ 17,400,000