Segment Reporting and Geographic Information - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 2,692	$ 2,499	$ 2,292	$ 2,075	$ 1,878	$ 1,707	$ 1,515	$ 1,354	$ 9,558	$ 6,454	$ 4,854
Long-Lived Assets	34,805				20,391				34,805	20,391	7,232
Leased vehicles, net	34,526				20,172				34,526	20,172	7,100
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									7,440	4,324	2,552
Long-Lived Assets	32,506				18,501				32,506	18,501	5,477
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									508	453	357
Long-Lived Assets	1,982				1,731				1,982	1,731	1,635
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									652	757	964
Long-Lived Assets	3				3				3	3	4
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									958	920	981
Long-Lived Assets	$ 314				$ 156				$ 314	$ 156	$ 116