Employee Benefit Plans - Postemployment Plan (Details) - Postemployment Retirement Benefits - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Net service cost	$ 6	$ 6
Interest cost	1	0
Amortization of prior service benefit	(1)	0
Amortization of actuarial gain	0	(1)
Net benefit cost	$ 6	$ 5