Leases (Other Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 52	$ 50
Operating cash flows from finance leases	3	2
Financing cash flows from finance leases	12	10
Leased assets obtained in exchange for new operating lease liabilities	48	75
Leased assets obtained in exchange for new finance lease liabilities	$ 34	$ 8