Employee Benefits - Net Pension Cost (Benefit) for All Funded and Unfunded Plans (Details) - Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	$ 6	$ 9
Expected return on plan assets	(7)	(10)
Amortization of losses	5	4
Settlement loss	0	4
Net pension cost	$ 4	$ 7