Repurchases of Common Stock (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Feb. 03, 2015
Summary Of Authorized Stock Repurchases [Roll Forward]
Authorized repurchase - as of January 1, 2014	$ 163,655,000
Additional board authorization		250,000,000
Proceeds from the exercise of stock options	339,000
Repurchases of common stock from open market	(40,708,000)
Authorized repurchase - as of March 31, 2015	$ 373,286,000