Debt (Schedule of Debt) (Details)		1 Months Ended					3 Months Ended	9 Months Ended
	Jun. 30, 2016 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) € / $	Sep. 30, 2016 USD ($) € / $	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Debt:							$ 14,863,000,000	$ 14,863,000,000		$ 15,770,000,000
Repayments of Long-term Debt								$ 7,320,000,000	$ 5,223,000,000
Senior Term Loan
Debt Instrument [Line Items]
Average interest rate (as a percent)							3.50%	3.50%
Nominal Unpaid Principal Balance	$ 700,000,000				$ 700,000,000		$ 698,000,000	$ 698,000,000		0
Senior Credit Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							0	0		0
Corporate Debt
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Net (Discount) Premium							(43,000,000)	(43,000,000)		(44,000,000)
Debt:							4,693,000,000	4,693,000,000		5,947,000,000
Senior Term Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							0	0		2,062,000,000
Senior ABL Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 0	$ 0		0
FCCR Number of Quarters							1 year
Promissory Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							7.00%	7.00%
Nominal Unpaid Principal Balance							$ 27,000,000	$ 27,000,000		27,000,000
Other Corporate Debt
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.51%	2.51%
Nominal Unpaid Principal Balance							$ 11,000,000	$ 11,000,000		2,000,000
HVF U.S. Vehicle Medium Term Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 970,000,000	$ 970,000,000		1,420,000,000
HVF Series 2010-1
Debt Instrument [Line Items]
Average interest rate (as a percent)							4.96%	4.96%
Nominal Unpaid Principal Balance							$ 115,000,000	$ 115,000,000		240,000,000
HVF 2011-1
Debt Instrument [Line Items]
Average interest rate (as a percent)							3.51%	3.51%
Nominal Unpaid Principal Balance							$ 230,000,000	$ 230,000,000		230,000,000
HVF 2013-1
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.91%	1.91%
Nominal Unpaid Principal Balance							$ 625,000,000	$ 625,000,000		950,000,000
HVF II U.S. ABS Program
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 2,229,000,000	$ 2,229,000,000		4,025,000,000
HVF II Series 2013-A
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.63%	1.63%
Nominal Unpaid Principal Balance							$ 1,483,000,000	$ 1,483,000,000		980,000,000
HVF II Series 2013-B
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.68%	1.68%
Nominal Unpaid Principal Balance							$ 746,000,000	$ 746,000,000		1,308,000,000
HVF II Series 2014-A
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							0	0		1,737,000,000
Repayments of Long-term Debt	$ 741,000,000				$ 820,000,000
HVF II U.S. Vehicle Medium Term Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 3,180,000,000	$ 3,180,000,000		1,380,000,000
HVF II Series 2015-1
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.93%	2.93%
Nominal Unpaid Principal Balance							$ 780,000,000	$ 780,000,000		780,000,000
HVF II Series 2015-2
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.30%	2.30%
Nominal Unpaid Principal Balance							$ 250,000,000	$ 250,000,000		250,000,000
HVF II Series 2015-3
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.96%	2.96%
Nominal Unpaid Principal Balance							$ 350,000,000	$ 350,000,000		350,000,000
HVF II Series 2016-1
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.72%	2.72%
Nominal Unpaid Principal Balance							$ 439,000,000	$ 439,000,000		0
HVF II Series 2016-2
Debt Instrument [Line Items]
Average interest rate (as a percent)							3.25%	3.25%
Nominal Unpaid Principal Balance							$ 561,000,000	$ 561,000,000		0
HVF II Series 2016-3
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.56%	2.56%
Nominal Unpaid Principal Balance							$ 400,000,000	$ 400,000,000		0
HVF II Series 2016-4
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.91%	2.91%
Nominal Unpaid Principal Balance							$ 400,000,000	$ 400,000,000		0
Fleet Debt
Debt Instrument [Line Items]
Unamortized Debt Issuance Costs and Net (Discount) Premium							(43,000,000)	(43,000,000)		(34,000,000)
Debt:							10,170,000,000	10,170,000,000		9,823,000,000
Donlen ABS Program
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 300,000,000	$ 300,000,000		370,000,000
HFLF Series 2013-2 Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.65%	1.65%
Nominal Unpaid Principal Balance							$ 300,000,000	$ 300,000,000		370,000,000
Repayments of Long-term Debt						$ 400,000,000
HFLF Medium Term Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 970,000,000	$ 970,000,000		853,000,000
HFLF Series 2013-A Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.34%	1.34%
Nominal Unpaid Principal Balance							$ 134,000,000	$ 134,000,000		270,000,000
HFLF Series 2014-1 Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.17%	1.17%
Nominal Unpaid Principal Balance							$ 179,000,000	$ 179,000,000		288,000,000
HFLF Series 2015-1 Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.20%	1.20%
Nominal Unpaid Principal Balance							$ 272,000,000	$ 272,000,000		295,000,000
HFLF Series 2016-1 Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.85%	1.85%
Nominal Unpaid Principal Balance							$ 385,000,000	$ 385,000,000		0
Other Fleet Debt
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 2,564,000,000	$ 2,564,000,000		1,809,000,000
US Vehicle RCF
Debt Instrument [Line Items]
Average interest rate (as a percent)							3.03%	3.03%
Nominal Unpaid Principal Balance							$ 193,000,000	$ 193,000,000		0
U.S. Fleet Financing Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 0	$ 0		190,000,000
European Revolving Credit Facility
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.11%	2.11%
Nominal Unpaid Principal Balance							$ 381,000,000	$ 381,000,000		273,000,000
European Fleet Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							4.29%	4.29%
Nominal Unpaid Principal Balance							$ 729,000,000	$ 729,000,000		464,000,000
Interest rate (as a percentage)							4.125%	4.125%
Foreign currency exchange rate (EURO to USD) | € / $							1.12	1.12
European Fleet Notes, 4.375%, Due January 2019
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 477,000,000	$ 477,000,000		464,000,000
Interest rate (as a percentage)							4.375%	4.375%
European Fleet Notes, 4.125%, Due October 2021
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 252,000,000	$ 252,000,000		0
Interest rate (as a percentage)							4.125%	4.125%
European Securitization
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.55%	1.55%
Nominal Unpaid Principal Balance							$ 474,000,000	$ 474,000,000		267,000,000
Canadian Securitization
Debt Instrument [Line Items]
Average interest rate (as a percent)							1.88%	1.88%
Nominal Unpaid Principal Balance							$ 267,000,000	$ 267,000,000		148,000,000
Australian Securitization
Debt Instrument [Line Items]
Average interest rate (as a percent)							3.12%	3.12%
Nominal Unpaid Principal Balance							$ 121,000,000	$ 121,000,000		98,000,000
Brazilian Fleet Financing
Debt Instrument [Line Items]
Average interest rate (as a percent)							17.63%	17.63%
Nominal Unpaid Principal Balance							$ 9,000,000	$ 9,000,000		7,000,000
New Zealand Revolving Credit Facility
Debt Instrument [Line Items]
Average interest rate (as a percent)							4.64%	4.64%
Nominal Unpaid Principal Balance							$ 31,000,000	$ 31,000,000		0
Capitalized Leases
Debt Instrument [Line Items]
Average interest rate (as a percent)							2.43%	2.43%
Nominal Unpaid Principal Balance							$ 359,000,000	$ 359,000,000		362,000,000
Senior Notes
Debt Instrument [Line Items]
Average interest rate (as a percent)							6.21%	6.21%
Nominal Unpaid Principal Balance							$ 4,000,000,000	$ 4,000,000,000		3,900,000,000
4.25% Senior Notes Due April 2018
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 250,000,000	$ 250,000,000		250,000,000
Interest rate (as a percentage)							4.25%	4.25%
7.50% Senior Notes due October 2018
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 0	$ 0		700,000,000
Repayments of debt				$ 700,000,000
Interest rate (as a percentage)				7.50%			7.50%	7.50%
7.50% Senior Notes due October 2018 | Forecast
Debt Instrument [Line Items]
Repayments of debt		$ 67,000,000
6.75% Senior Notes due April 2019
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 1,250,000,000	$ 1,250,000,000		1,250,000,000
Interest rate (as a percentage)							6.75%	6.75%
5.875% Senior Notes due October 2020
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 700,000,000	$ 700,000,000		700,000,000
Interest rate (as a percentage)							5.875%	5.875%
7.375% Senior Notes due January 2021
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 500,000,000	$ 500,000,000		500,000,000
Interest rate (as a percentage)							7.375%	7.375%
6.25% Senior Notes due October 2022
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 500,000,000	$ 500,000,000		500,000,000
Interest rate (as a percentage)							6.25%	6.25%
5.50% Senior Notes due October 2024
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance							$ 800,000,000	$ 800,000,000		$ 0
Interest rate (as a percentage)							5.50%	5.50%
Subsequent Event | 6.75% Senior Notes due April 2019
Debt Instrument [Line Items]
Repayments of debt			$ 800,000,000
Interest rate (as a percentage)			6.75%