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, 2023	Dec. 31, 2022
Actual return on plan assets:
Balance at the beginning of the period	$ 3,537	$ 6,246
Foreign exchange	196	(559)
Balance at the end of the period	3,775	3,537
Significant Unobservable Inputs (Level 3)
Actual return on plan assets:
Balance at the beginning of the period	1,403	2,305
Relating to assets still held at the end of the year	30	(674)
Purchases, sales and settlements-net	0	0
Foreign exchange	77	(228)
Balance at the end of the period	$ 1,510	$ 1,403