Income Taxes - Reconciliation of Total Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of unrecognized tax benefits
Unrecognized tax benefits balance at January 1	$ 1,166	$ 1,037	$ 926
Gross increase for tax positions taken during a prior year	98	97	151
Gross decrease for tax positions taken during a prior year	(18)	(1)	(168)
Gross increase for tax positions taken during the current year	52	38	291
Settlement with taxing authorities	(6)	(3)	(163)
Lapse of statute of limitations	(3)	(2)	0
Unrecognized tax benefits balance at December 31	$ 1,289	$ 1,166	$ 1,037