Employee Benefits - Schedule of changes in Level 3 fair value for U.K. Pension Plans (Details) - Pension Plan - U.K. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Actual return on plan assets:
Balance at the beginning of the period	$ 6,652	$ 5,959
Foreign exchange	(76)	283
Balance at the end of the period	6,246	6,652
Significant Unobservable Inputs (Level 3)
Actual return on plan assets:
Balance at the beginning of the period	2,625	1,849
Relating to assets still held at the end of the year	(286)	13
Purchases, sales and settlements-net	0	682
Foreign exchange	(34)	81
Balance at the end of the period	$ 2,305	$ 2,625