Pension and Other Postretirement Employee Benefit Plans - Changes In Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Investments classified in level 3 of the valuation hierarchy	$ 19,890	$ 25,692
Unrealized gains (losses)	(501)	332
Decrease for settlements	54	94
Level 3
Defined Benefit Plan Disclosure [Line Items]
Investments classified in level 3 of the valuation hierarchy	$ 2,613	$ 3,172