Debt (Narrative) (Details)		1 Months Ended						9 Months Ended
	Jun. 30, 2016 USD ($)	Jan. 31, 2018 USD ($)	Sep. 30, 2016 USD ($)	Aug. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Apr. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 GBP (£)	Sep. 30, 2016 EUR (€)	Sep. 30, 2016 NZD	Sep. 30, 2016 USD ($)	Jun. 30, 2016 EUR (€)	Jun. 30, 2016 GBP (£)	Jun. 30, 2016 USD ($)	Feb. 24, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of vehicle debt								$ 7,665,000,000	$ 6,069,000,000
Redemption Price, Percentage					1.875%
Repayments of Long-term Debt								7,320,000,000	5,223,000,000
Repayments of Principal in Next Twelve Months														$ 3,200,000,000
Availability under borrowing base limitation														1,117,000,000
VIE, total assets														677,000,000					$ 418,000,000
VIE, total liabilities														677,000,000					418,000,000
Letters of credit
Debt Instrument [Line Items]
Outstanding standby letters of credit														614,000,000
Eliminations
Debt Instrument [Line Items]
Proceeds from issuance of vehicle debt								0	0
Repayments of Long-term Debt								$ 0	$ 0
Senior Term Facility
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost						$ 20,000,000
7.50% Senior Notes due October 2018
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost					$ 6,000,000
Repayments of debt					700,000,000
Redemption premium					$ 13,000,000
Nominal Unpaid Principal Balance														$ 0					700,000,000
Interest rate (as a percentage)					7.50%							7.50%	7.50%	7.50%
Repayments of Other Debt					$ 25,000,000
Interest paid					$ 12,000,000
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
Interest rate (as a percentage)												6.75%	6.75%	6.75%
Senior Term Loan
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														$ 698,000,000			$ 700,000,000		0
Senior Term Loan | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis Spread on Variable Rate						0.75%
5.50% Senior Notes due October 2024
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														$ 800,000,000					0
Proceeds from issuance of vehicle debt			$ 800,000,000
Interest rate (as a percentage)												5.50%	5.50%	5.50%
Revolving Credit Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance																	1,700,000,000
HVF II Series 2016-1 Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance																		$ 1,100,000,000
European Revolving Credit Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														$ 381,000,000					273,000,000
Availability under borrowing base limitation														0
European Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Borrowing Capacity | €															€ 340,000,000
European Revolving Credit Facility | Revolving Credit Facility | Forecast
Debt Instrument [Line Items]
Maximum Borrowing Capacity | €										€ 250,000,000
European Fleet Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														$ 729,000,000					464,000,000
Interest rate (as a percentage)												4.125%	4.125%	4.125%
Maximum Borrowing Capacity | €												€ 225,000,000
Senior ABL Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														$ 0					0
Availability under borrowing base limitation														1,100,000,000
Senior ABL Facility | Letters of credit
Debt Instrument [Line Items]
Availability under borrowing base limitation														400,000,000
Senior Credit Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														0					0
Outstanding standby letters of credit														600,000,000
HFLF Series 2013-2 Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														300,000,000					370,000,000
Repayments of Long-term Debt							$ 400,000,000
US Vehicle RCF
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														193,000,000					0
Availability under borrowing base limitation														4,000,000
Outstanding standby letters of credit														1,000,000,000
US Vehicle RCF | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Borrowing Capacity																	200,000,000
HVF II Series 2014-A Notes, Class A
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance				$ 20,000,000
Repayments of Long-term Debt				500,000,000		$ 1,800,000,000
Availability under borrowing base limitation																	500,000,000
HVF II Series 2013-B Notes, Class B
Debt Instrument [Line Items]
Repayments of Long-term Debt				330,000,000		20,000,000
Availability under borrowing base limitation																	55,000,000
HVF II Series 2014-A Notes, Class B
Debt Instrument [Line Items]
Repayments of Long-term Debt				20,000,000		20,000,000
Availability under borrowing base limitation																	20,000,000
HVF II Series 2013-B
Debt Instrument [Line Items]
Availability under borrowing base limitation																	1,000,000,000
Debt Instrument, Commitments Transferred																	500,000,000
HVF II Series 2014-A
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost				$ 1,000,000
Nominal Unpaid Principal Balance														0					1,737,000,000
Repayments of Long-term Debt	$ 741,000,000					820,000,000
HVF II Series 2013-A
Debt Instrument [Line Items]
Availability under borrowing base limitation																	2,200,000,000
HVF II Series 2016-3 Notes And HVF II Series 2016-4 Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance																	848,000,000
HVF II Series 2016-3 Notes, Class D
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 48,000,000
HFLF Series 2016-1 Notes
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														385,000,000					0
Proceeds from issuance of vehicle debt							400,000,000
European Securitization
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														474,000,000					267,000,000
Availability under borrowing base limitation														3,000,000
Maximum Borrowing Capacity | €															€ 460,000,000
UK Leveraged Financing
Debt Instrument [Line Items]
Maximum Borrowing Capacity | £																£ 300,000,000
UK Leveraged Financing | Forecast
Debt Instrument [Line Items]
Maximum Borrowing Capacity | £											£ 250,000,000
New Zealand Revolving Credit Facility
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance														31,000,000					$ 0
Availability under borrowing base limitation														$ 6,000,000
Maximum Borrowing Capacity | NZD													NZD 60,000,000
Affiliated Entity | HVF II Series 2016-2 Notes, Class D | Eliminations
Debt Instrument [Line Items]
Nominal Unpaid Principal Balance																		$ 61,000,000
Affiliated Entity | HVF II Series 2015-3 Notes, Class D | Eliminations
Debt Instrument [Line Items]
Proceeds from issuance of vehicle debt							$ 15,000,000
Level 1 | Prepaid Expenses and Other Assets | CAR, Inc
Debt Instrument [Line Items]
Equity Method Investments, Fair Value Disclosure																	$ 264,000,000