Leases (Contractual Maturities of Operating Lease Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt and Lease Obligation [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 60
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Two	57
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Three	51
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Four	46
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Five	40
Lessee, Operating Lease, Liability, Payments, Due after Rolling Year Five	149
Operating lease contractual maturities	403
Operating lease imputed interest	(59)
Operating lease liabilities	$ 344	$ 367