Shareholders' equity Share Repurchases (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 27, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 19, 2021	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			0		2,266,150
Cost of shares repurchased			$ 0		$ 326
Repurchase authorization remaining at end of period			$ 1,124		$ 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				22,877,400
Cost of shares repurchased				$ 3,956
CB_Increase(Decrease)StockRepurchaseProgramAuthorizedAmount							$ 1,000
July 2021 Stock Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount						$ 5,000
Number of shares repurchased		8,412,000
Cost of shares repurchased		$ 1,516
Repurchase authorization remaining at end of period		$ 3,551		$ 3,551
Subsequent Event [Member] | July 2021 Stock Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased	167,700
Cost of shares repurchased	$ 29
Repurchase authorization remaining at end of period	$ 3,522