Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ 1	$ 3
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	12	12
Expected return on plan assets	(20)	(23)
Recognized net actuarial loss	13	14
Settlements	1	3
Net periodic benefit	7	7
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Recognized net actuarial loss	0	0
Amortization of prior service benefit	(2)	(1)
Net periodic benefit	$ (1)	$ 0