Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Nov. 30, 2018
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 1,100,000,000
Repurchases of common stock	$ (81,400,000)		$ (116,247,000)	$ (185,512,000)
Amortization expense from capitalized stock-based compensation	$ 7,300,000	$ 5,800,000	$ 15,400,000	$ 11,400,000
Common Stock
Class of Stock [Line Items]
Shares repurchased during period (in shares)	1.1		1.5