Shareholders' equity Share Repurchases (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 29, 2021	Mar. 31, 2021	Mar. 31, 2020	Feb. 01, 2021	Nov. 19, 2020	Nov. 21, 2019
Nov 2019 Stock Repurchase Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 1,500
Number of shares repurchased			2,266,150
Cost of shares repurchased			$ 326
Repurchase authorization remaining at end of period			$ 1,124
Nov 2020 Stock Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 2,500	$ 1,500
Number of shares repurchased		3,110,000
Cost of shares repurchased		$ 519
Repurchase authorization remaining at end of period		$ 1,982
CB_Increase(Decrease)StockRepurchaseProgramAuthorizedAmount				$ 1,000
Subsequent Event [Member] | Nov 2020 Stock Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	450,000
Cost of shares repurchased	$ 76
Repurchase authorization remaining at end of period	$ 1,906