Significant Accounting Policies - Additional Information (Detail) $ in Millions		12 Months Ended
	Jan. 01, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2017 EUR (€)	Sep. 30, 2016	Jun. 30, 2015 EUR (€)
Significant Accounting Policies [Line Items]
Deferred revenue		$ 364	$ 326
Effect on retained earnings		517	331
Effect on AOCI		$ (220)	$ (149)
2.5% Senior Notes Due 2022
Significant Accounting Policies [Line Items]
Senior unsecured notes principal amount | €					€ 650,000,000	€ 650,000,000		€ 650,000,000
Senior notes, interest rate		2.50%	2.50%		2.50%	2.50%	2.50%	2.50%
Stock Options
Significant Accounting Policies [Line Items]
Vesting period		4 years
Minimum
Significant Accounting Policies [Line Items]
Definite lived intangible assets, estimated useful life		1 year
Minimum | RSUs
Significant Accounting Policies [Line Items]
Vesting period		3 years
Maximum
Significant Accounting Policies [Line Items]
Definite lived intangible assets, estimated useful life		12 years
Maximum | RSUs
Significant Accounting Policies [Line Items]
Vesting period		4 years
Computer equipment | Minimum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives		3 years
Computer equipment | Maximum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives		5 years
Software Development | Minimum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			3 years
Software Development | Maximum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			5 years
Furniture and other equipment | Minimum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			3 years
Furniture and other equipment | Maximum
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives			5 years
ASU 2014-09
Significant Accounting Policies [Line Items]
Effect on retained earnings	$ 323
Long-term investments and other assets	842
ASU 2016-16
Significant Accounting Policies [Line Items]
Effect on retained earnings	26
Long-term investments and other assets	31
Deferred tax assets, net	5
ASU 2018-02
Significant Accounting Policies [Line Items]
Tax cuts and jobs act, reclassification from AOCI to retained earnings, tax effect	10
ASU 2016-02 | Forecast
Significant Accounting Policies [Line Items]
Effect on retained earnings				$ 10
Operating lease, right-of-use asset				570
Operating lease, right-of-use asset, gross				620
Existing lease incentives and deferred rent				50
Operating lease, liability				$ 620
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | ASU 2014-09
Significant Accounting Policies [Line Items]
Effect on retained earnings before tax impact	11
Effect on retained earnings	(8)
Effect on loyalty program before tax impact	49
Effect on loyalty program	38
Immaterial adjustments before tax impact	2
Immaterial adjustments	1
Effect on variable consideration before tax impact	40
Effect on variable consideration	31
Long-term investments and other assets	(3)
Deferred Merchant Bookings
Significant Accounting Policies [Line Items]
Deferred merchant bookings liability, current	3,219	$ 3,627
Deferred merchant booking liability, decrease due to recognition during period		2,898
Contract with customer, liability, revenue recognized		421
Deferred Loyalty Rewards
Significant Accounting Policies [Line Items]
Deferred merchant bookings liability, current	619	$ 700
Deferred Loyalty Rewards | Minimum
Significant Accounting Policies [Line Items]
Customer loyalty program, period of recognition		1 year
Deferred Loyalty Rewards | Maximum
Significant Accounting Policies [Line Items]
Customer loyalty program, period of recognition		2 years
Other Deferred Revenue
Significant Accounting Policies [Line Items]
Contract with customer, liability, revenue recognized		$ 288
Deferred revenue	326	$ 364
Despegar.com Corp. | ASU 2016-01
Significant Accounting Policies [Line Items]
Effect on retained earnings	7
Effect on AOCI	$ 7