Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2014	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Feb. 29, 2016
Class of Stock [Line Items]
Stock repurchase program, authorized amount						$ 1,000,000,000.0
Repurchases of common stock	$ (62,000,000)			$ (177,615,000)	$ (199,710,000)
Amortization expense from capitalized stock-based compensation		$ 3,900,000	$ 3,600,000	$ 7,400,000	$ 6,900,000
Common Stock [Member]
Class of Stock [Line Items]
Shares repurchased during period (in shares)				3.1