Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	$ 9,028
Lessee, Lease, Description [Line Items]
Vehicle Lease Charges	$ 255	$ 253	$ 222
Supplemental balance sheet information related to leases [Line Items]
Document Period End Date	Dec. 31, 2019
Operating Lease, Residual Value of Leased Asset	$ 314
Operating Lease, Right-of-Use Asset	2,596	0
Operating Lease, Liability, Current	479	0
Operating Lease, Liability, Noncurrent	2,140	$ 0
Americas [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	6,303
EMEA [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	2,141
Asia and Australasia [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	584
Avis [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	5,163
Budget [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	3,129
Other Brands [Member]
Disaggregation of Revenue [Line Items]
Operating Lease, Lease Income	736
Property leases [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	722
Variable Lease, Cost	274
Sublease Income	(8)
Lease, Cost	$ 988
Supplemental balance sheet information related to leases [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	8 years 10 months 24 days
Operating Lease, Right-of-Use Asset	$ 2,596
Operating Lease, Liability, Noncurrent	2,140
Operating Lease, Liability	$ 2,619
Operating Lease, Weighted Average Discount Rate, Percent	4.31%
Supplemental cash flow information related to leases [Line Items]
Operating Lease, Payments	$ 733
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	531
Maturities of lease liabilities [Line Items]
Lessee, Operating Lease, Liability, Payments, Due Next Rolling Twelve Months	580
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Two	470
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Three	400
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Four	348
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Five	230
Lessee, Operating Lease, Liability, Payments, Due after Rolling Year Five	1,174
Lessee, Operating Lease, Liability, Payments, Due	3,202
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	583
Vehicle leases [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	301
Finance Lease, Right-of-Use Asset, Amortization	42
Finance Lease, Interest Expense	$ 4
Supplemental balance sheet information related to leases [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	1 year 9 months 18 days
Operating Lease, Right-of-Use Asset	$ 195
Operating Lease, Liability, Current	124
Operating Lease, Liability, Noncurrent	71
Operating Lease, Liability	$ 195
Operating Lease, Weighted Average Discount Rate, Percent	3.08%
Finance Lease, Right-of-Use Asset, Gross	$ 337
Finance Lease, Right-of-Use Asset, Accumulated Amortization	(56)
Finance Lease, Right-of-Use Asset	281
Finance Lease, Liability, Current	95
Finance Lease, Liability, Noncurrent	157
Finance Lease, Liability	$ 252
Finance Lease, Weighted Average Remaining Lease Term	2 years
Finance Lease, Weighted Average Discount Rate, Percent	1.67%
Supplemental cash flow information related to leases [Line Items]
Operating Lease, Payments	$ 248
Finance Lease, Interest Payment on Liability	4
Finance Lease, Principal Payments	266
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	262
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	304
Maturities of lease liabilities [Line Items]
Lessee, Operating Lease, Liability, Payments, Due Next Rolling Twelve Months	128
Finance Lease, Liability, Payments, Due in Next Rolling Twelve Months	95
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Two	51
Finance Lease, Liability, Payments, Due in Rolling Year Two	29
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Three	17
Finance Lease, Liability, Payments, Due in Rolling Year Three	127
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Four	5
Finance Lease, Liability, Payments, Due in Rolling Year Four	1
Lessee, Operating Lease, Liability, Payments, Due in Rolling Year Five	0
Finance Lease, Liability, Payments, Due in Rolling Year Five	0
Lessee, Operating Lease, Liability, Payments, Due after Rolling Year Five	0
Finance Lease, Liability, Payments, Due in Rolling after Year Five	0
Lessee, Operating Lease, Liability, Payments, Due	201
Finance Lease, Liability, Payment, Due	252
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	6
Finance Lease, Liability, Undiscounted Excess Amount	$ 0