Repurchases of Common Stock (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Feb. 03, 2015	Jan. 01, 2015
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase	$ 353,422,000	$ 353,422,000		$ 163,655,000
Additional board authorization			$ 250,000,000
Proceeds from the exercise of stock options		2,498,000
Repurchase of common stock from open market	$ (22,023,000)	$ (62,731,000)