Stockholders' Equity - Repurchases of Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 29, 2020	Jan. 28, 2016
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 1,749	$ 2,900	$ 954
Stock Repurchase, Average Cost Per Share	$ 66.36	$ 72.95	$ 71.79
2016 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 12,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 3,400
Publicly Announced Program [Member]
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	26	40	13
Subsequent Event [Member] | 2020 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 5,000