Employee Benefits - Net Pension Cost (Benefit) for All Funded and Unfunded Plans (Details) - Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	$ 6	$ 9	$ 18	$ 26
Expected return on plan assets	(7)	(10)	(21)	(29)
Amortization of losses	5	5	14	13
Settlement loss	7	0	7	8
Net pension cost	$ 11	$ 4	$ 18	$ 18