Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Oct. 31, 2013
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount						$ 750,000,000
Shares repurchased during period (in shares)				1.8
Repurchases of common stock	$ 62,000,000			$ 126,068,000	$ 187,491,000
Amortization expense from capitalized stock-based compensation		$ 3,400,000	$ 2,000,000	$ 6,400,000	$ 3,900,000