Employee Benefits - Amounts recognized in Accumulated other comprehensive loss that have not yet been recognized (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
U.S.
Amounts recognized in Accumulated other comprehensive loss unrecognized as components of net periodic benefit cost
Net loss	$ 1,551	$ 1,812
Prior service cost (income)	0	0
Net amount recognized	1,551	1,812
U.K.
Amounts recognized in Accumulated other comprehensive loss unrecognized as components of net periodic benefit cost
Net loss	1,215	1,286
Prior service cost (income)	40	43
Net amount recognized	1,255	1,329
Other
Amounts recognized in Accumulated other comprehensive loss unrecognized as components of net periodic benefit cost
Net loss	489	521
Prior service cost (income)	(6)	(7)
Net amount recognized	$ 483	$ 514