Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended
	Jul. 26, 2018	Jun. 30, 2018	Apr. 26, 2018	Feb. 28, 2015
Payments for Repurchase of Equity [Abstract]
Authorized share repurchase			15,000,000	10,000,000
Stock repurchased, shares		3,700,000
Stock repurchased, value		$ 409
Average repurchase price per share (in dollars per share)		$ 110.61
Shares authorized and remaining under the repurchase program		16,200,000
Subsequent Event
Payments for Repurchase of Equity [Abstract]
Stock repurchased, shares	300,000
Stock repurchased, value	$ 42
Average repurchase price per share (in dollars per share)	$ 124.95