Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Nov. 06, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Apr. 26, 2018
Equity, Class of Treasury Stock [Line Items]
Treasury stock (in shares)		123,586,000		123,586,000		97,159,000
Authorized share repurchase							15,000,000
Stock repurchases (in shares)				2,300,000
Stock repurchased, value		$ 300	$ 193	$ 300	$ 602
Average repurchase price per share (in dollars per share)				$ 130.30
Shares authorized and remaining under the repurchase program		9,900,000		9,900,000
Common stock
Equity, Class of Treasury Stock [Line Items]
Treasury stock (in shares)		116,300,000		116,300,000		97,200,000
Class B Common Stock
Equity, Class of Treasury Stock [Line Items]
Treasury stock (in shares)		7,300,000		7,300,000
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Stock repurchases (in shares)	900,000
Stock repurchased, value	$ 118
Average repurchase price per share (in dollars per share)	$ 135.58