Stockholders' Equity Stock Repurchase Program (Details) - 2016 Stock Repurchase Program - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 28, 2016
Equity, Class of Treasury Stock [Line Items]
Authorized amount					$ 12,000
Repurchases of common stock (in shares)	3	6	25	26
Repurchases of common stock, amount	$ 223	$ 449	$ 1,600	$ 1,900
Remaining authorized repurchase amount	$ 3,500		$ 3,500