Employee Benefits - Net Pension Cost (Benefit) for All Funded and Unfunded Plans (Details) - Pension Plans [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	$ 11	$ 10
Expected return on plan assets	(12)	(13)
Amortization of losses	4	4
Net pension/postretirement benefit cost	$ 3	$ 1