Employee Benefit Plans - MEC (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Plan | United States
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 7	$ 4	$ 22	$ 11
Interest cost	21	23	59	69
Expected return on plan assets	(32)	(35)	(101)	(105)
Net amortization	6	8	19	25
Net periodic benefit cost (credit)	6	0	3	0
Pension Plan | United States | MEC
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	2	15	4
Interest cost	6	7	17	19
Expected return on plan assets	(9)	(10)	(28)	(30)
Net amortization	0	0	1	1
Net periodic benefit cost (credit)	2	(1)	5	(6)
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	8	5
Interest cost	4	6	14	16
Expected return on plan assets	(5)	(9)	(16)	(25)
Net amortization	0	(1)	(2)	(5)
Net periodic benefit cost (credit)	1	(3)	4	(9)
Other Postretirement Plans | MEC
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	6	3
Interest cost	2	2	6	5
Expected return on plan assets	(2)	(4)	(7)	(10)
Net amortization	(1)	(1)	(3)	(4)
Net periodic benefit cost (credit)	$ 1	$ (2)	$ 2	$ (6)