Stockholders' Equity Stock Repurchase Program (Details) - 2016 Stock Repurchase Program - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 28, 2016
Equity, Class of Treasury Stock [Line Items]
Authorized amount					$ 12,000
Repurchases of common stock (in shares)	9	7	21	20
Repurchases of common stock, amount	$ 588	$ 450	$ 1,400	$ 1,500
Remaining authorized repurchase amount	$ 3,700		$ 3,700