Stockholders' Equity - Summary of Repurchase Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2019	Jan. 31, 2018
Equity [Abstract]
Shares Repurchased	134,000,000
Average Price per Share (in usd per share)	$ 37.26
Value of Shares Repurchased	$ 5,000,000,000
Shares Repurchased, Remaining Amount Authorized
Beginning balance	3,151,000,000
Repurchase of shares of common stock	(5,000,000,000)
Ending balance	$ 2,151,000,000
Treasury shares retired	0
Stock Repurchase Program January 2018
Shares Repurchased, Remaining Amount Authorized
Authorization of additional plan in January 2019			$ 6,000,000,000.0
Stock Repurchase Program January 2019
Shares Repurchased, Remaining Amount Authorized
Authorization of additional plan in January 2019		$ 4,000,000,000