Stockholders' Equity - Repurchase Authorizations (Details) - USD ($) shares in Millions	9 Months Ended
	Sep. 30, 2017	Jan. 28, 2016
Equity, Class of Treasury Stock [Line Items]
Repurchases of common stock, amount	$ 934,000,000
2016 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Authorized amount		$ 12,000,000,000.0
Repurchases of common stock (in shares)	12
Repurchases of common stock, amount	$ 848,000,000
Remaining authorized repurchase amount	$ 8,200,000,000