Employee Benefit Plans - PAC (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4	$ 3	$ 6	$ 4
Interest cost	5	4	10	10
Expected return on plan assets	(6)	(7)	(11)	(16)
Net amortization	(1)	(3)	(2)	(4)
Net periodic benefit credit	2	(3)	3	(6)
PAC | Other Postretirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1	1
Interest cost	2	2	4	5
Expected return on plan assets	(2)	(3)	(4)	(7)
Net amortization	0	0	0	0
Net periodic benefit credit	1	0	1	(1)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	8	4	15	7
Interest cost	18	23	38	46
Expected return on plan assets	(36)	(35)	(69)	(70)
Net amortization	7	8	13	17
Net periodic benefit credit	(3)	0	(3)	0
United States | PAC | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	7	9	14	18
Expected return on plan assets	(14)	(14)	(27)	(28)
Net amortization	5	4	10	9
Net periodic benefit credit	$ (2)	$ (1)	$ (3)	$ (1)