Pensions and Other Benefits - Details of Net Periodic Benefit Costs Related to Pension and Other Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of net periodic benefit cost:
Net periodic benefit cost (credits)	$ (45)	$ (25)	$ 91
Pension Benefits
Components of net periodic benefit cost:
Service cost	53	51	44
Interest cost	163	193	237
Expected return on plan assets	(361)	(333)	(324)
Amortization - prior service costs (credits)	2	2	2
Amortization - actuarial losses	132	145	132
Net periodic benefit cost, excluding below	(11)	58	91
Multiemployer plans (a)	75	76	77
Settlement, termination and curtailment losses	135	11	11
Net periodic benefit cost (credits)	199	145	179
Other Benefits
Components of net periodic benefit cost:
Service cost	11	12	13
Interest cost	50	63	91
Expected return on plan assets	(81)	(80)	(79)
Amortization - prior service costs (credits)	(29)	(6)	29
Amortization - actuarial losses	(23)	(16)	3
Net periodic benefit cost, excluding below	(72)	(27)	57
Multiemployer plans (a)	0	0	0
Settlement, termination and curtailment losses	19	4	0
Net periodic benefit cost (credits)	$ (53)	$ (23)	$ 57