Leases (Supplemental Cash Flow Information Related to Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating cash flows related to operating leases	$ 162	$ 147
Operating cash flows related to financing leases	5	5
Financing cash flows related to finance leases	10	9
Right of use asset obtained in exchange for operating lease liability	179	162
Right of use asset obtained in exchange for finance lease liability	$ 11	$ 11