Equity - Summary of Common Stock Purchases (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Equity, Class of Treasury Stock [Line Items]
Shares of common stock purchased	0	213	[1]	307	[2]
Cost of purchase	$ 0	$ 8,865	[1]	$ 12,198	[2]
Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Cost of purchase		$ 2,100		$ 8,200

[1] Represents shares purchased pursuant to the ASR with Goldman Sachs & Co. LLC entered into in February 2019, as well as open market share repurchases of $2.1 billion

[2] Represents shares purchased pursuant to the ASR with Citibank entered into in March 2018, as well as open market share repurchases of $8.2 billion