Leases (Lease Income Associated with Operating Leases) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Fixed payments	$ 17	$ 17	$ 50	$ 51
Variable payments	43	40	82	92
Total lease income under operating leases	$ 60	$ 57	$ 132	$ 143