Equity - Stock Repurchases (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($) transaction shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Jan. 29, 2020 shares	Dec. 04, 2013 shares
Equity, Class of Treasury Stock [Line Items]
ARS agreement transactions | transaction			2
Total cash utilized | $			$ 0	$ 1,164	$ 1,240
Accelerated Share Repurchases, October 2018, Received Subsequently
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)					400,000
Accelerated Share Repurchases, October 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)					5,900,000
Total cash utilized | $					$ 1,240
2020 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares authorized to be repurchased (shares)						30,000,000
Shares authorized to be repurchased as percentage of outstanding common stock						12.00%
Remaining shares available under repurchase program (shares)			30,000,000
2013 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares authorized to be repurchased (shares)							50,000,000
Shares authorized to be repurchased as percentage of outstanding common stock							18.00%
Remaining shares available under repurchase program (shares)			800,000
Stock Repurchases
Equity, Class of Treasury Stock [Line Items]
Stock repurchased during period (shares)				4,000,000
Total cash utilized | $		$ 3		$ 1,161
Stock Repurchases, subsequently settled
Equity, Class of Treasury Stock [Line Items]
Total cash utilized | $	$ 1,164