Leasing Leasing (Depreciation Expense on Operating Lease Assets) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Leases, Operating [Abstract]
Operating lease revenue	$ 361	$ 382
Depreciation expense on operating lease assets	261	291
Remarketing (gains) and losses, net	(15)	(18)
Net depreciation expense on operating lease assets	$ 246	$ 273