Equity - Stock Repurchases (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 29, 2020	Dec. 04, 2013
Share repurchases
Total cash utilized		$ 3	$ 1,164	$ 1,240	$ 1,660
Stock repurchased during period (shares)	400,000		4,000,000.0	5,900,000	8,400,000
2020 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program number of shares authorized to be repurchased (shares)						30,000,000
Maximum number of shares authorized for repurchase under stock repurchase plan as percentage of outstanding common stock (as a percent)						12.00%
Remaining shares available under repurchase program (shares)			30,000,000
Share repurchases
Total cash utilized			$ 1,161
2013 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program number of shares authorized to be repurchased (shares)							50,000,000
Maximum number of shares authorized for repurchase under stock repurchase plan as percentage of outstanding common stock (as a percent)							18.00%
Remaining shares available under repurchase program (shares)			800,000
Stock Repurchases
Share repurchases
Total number of shares purchased (shares)			500,000	1,200,000	900,000
Average price paid per share (USD per share)			$ 295.40	$ 208.83	$ 182.93
Total cash utilized			$ 161	$ 240	$ 160