Stockholders' Equity (Details) - USD ($) shares in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Aug. 10, 2018	May 02, 2018
Equity [Abstract]
Stock repurchase program, authorized amount				$ 750,000,000	$ 500,000,000
Treasury stock, shares, acquired (in shares)	28		31
Payments for repurchase of common stock	$ 280,000,000	$ 0	$ 311,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 439,000,000