Leasing (Depreciation Expense on Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease revenue	$ 393	$ 360	$ 1,147	$ 1,070
Depreciation expense on operating lease assets	225	246	662	737
Remarketing gains, net	(86)	(71)	(278)	(62)
Net depreciation expense on operating lease assets	139	175	384	675
Variable lease payments, excessive wear and tear	$ 3	$ 6	$ 13	$ 18