Share-based compensation (Pre-tax and After-tax Share-based Compensation Expense) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based Payment Arrangement, Expense, Tax Benefit		$ 19	$ 10	$ 12
Restricted stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense, pre-tax		210	210	224
Share-based compensation expense, after-tax		164	164	180
Stock options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense, pre-tax		55	45	42
Share-based compensation expense, after-tax	[1]	$ 36	$ 38	$ 39

[1] The windfall tax benefit recorded to Income tax expense in the Consolidated statement of operations was $19 million, $10 million, and $12 million for the years ended December 31, 2021, 2020, and 2019, respectively.