Segment Reporting and Geographic Information - Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,878	$ 1,707	$ 1,515	$ 1,354	$ 1,305	$ 1,261	$ 1,191	$ 1,097	$ 6,454	$ 4,854	$ 3,344
Long-lived assets	20,391				7,232				20,391	7,232	3,515
Leased vehicles, net	20,172				7,060				20,172	7,060	3,400
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									4,324	2,552	2,185
Long-lived assets	18,501				5,477				18,501	5,477	2,472
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									453	357	204
Long-lived assets	1,731				1,635				1,731	1,635	965
Brazil [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									757	964	234
Long-lived assets	3				4				3	4	4
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									920	981	721
Long-lived assets	$ 156				$ 116				$ 156	$ 116	$ 74