Leasing (Depreciation Expense on Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease revenue	$ 384	$ 343	$ 754	$ 710
Depreciation expense on operating lease assets	210	241	437	491
Remarketing (gains) losses, net	(128)	11	(192)	9
Net depreciation expense on operating lease assets	82	252	245	500
Variable lease payments, excessive wear and tear	$ 5	$ 5	$ 10	$ 12