Summary of Significant Accounting Policies - Summary of the Components of Income from Leveraged Leases (Details) - Domestic and international leveraged leases - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Leveraged Lease [Line Items]
Pretax leveraged lease income	$ 25	$ 25	$ 25
Net impact of Tax Reform Legislation	0	48	0
Income tax expense	(6)	(9)	(9)
Net leveraged lease income	$ 19	$ 64	$ 16