Stockholders’ Equity - Summary of Stock Repurchase Activity (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Feb. 13, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 31, 2020
Equity [Abstract]
Shares Repurchased (in shares)				42,000,000
Average Price per Share (in usd per share)				$ 40.59
Value of Shares Repurchased				$ 1,698
Shares Repurchased, Remaining Amount Authorized
Beginning balance				2,151
Authorization of additional plan						$ 5,000
Repurchase of shares of common stock				(1,698)
Ending balance		$ 2,453		$ 2,453
Treasury shares retired (in shares)				0
Treasury stock at cost
Equity [Abstract]
Value of Shares Repurchased		1,150	$ 1,000	$ 4,700	$ 4,002
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock		(1,150)	(1,000)	(4,700)	(4,002)
Additional paid-in capital
Equity [Abstract]
Value of Shares Repurchased		(450)	0	0	0
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock		450	$ 0	$ 0	$ 0
Accelerated Share Repurchased Agreement
Equity [Abstract]
Shares Repurchased (in shares)	69,000,000
Value of Shares Repurchased	$ 3,000
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock	(3,000)
Accelerated Share Repurchased Agreement | Treasury stock at cost
Equity [Abstract]
Shares Repurchased (in shares)				74,000,000
Average Price per Share (in usd per share)				$ 40.77
Value of Shares Repurchased	2,550	450		$ 3,000
Shares Repurchased, Remaining Amount Authorized
Repurchase of shares of common stock	$ (2,550)	$ (450)		$ (3,000)