Leases (Supplemental Cash Flow and Other Information Related to Leases) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases	$ 47	$ 35
Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases	2	2
Cash paid for amounts included in the measurement of lease liabilities: Financing cash flows from finance leases	1	3
Right-of-use assets obtained in exchange for new finance lease liabilities	17	1
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 35	$ 15