Leasing (Depreciation Expense on Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases, Operating [Abstract]
Operating Lease, Lease Income	$ 360	$ 368	$ 1,070	$ 1,092
Depreciation expense on operating lease assets	246	262	737	785
Remarketing gains, net	(71)	(28)	(62)	(66)
Net depreciation expense on operating lease assets	175	234	675	719
Variable lease payments, excessive wear and tear	$ 6	$ 5	$ 18	$ 14