Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 EUR (€)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 EUR (€)	Jan. 01, 2018 USD ($)	Jun. 30, 2015 EUR (€)
Significant Accounting Policies [Line Items]
Prepaid merchant bookings	$ 226	$ 26
Operating lease right-of-use assets	611	0
Operating lease, liability	651
Deferred revenue	$ 321	364
Definite lived intangible assets, estimated useful life	1 year
Advertising expense	$ 3,500	$ 3,400	$ 3,300
Effect of retained earnings					$ 6		$ (34)
2.5% (€650 million) 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%
Stock Options
Significant Accounting Policies [Line Items]
Vesting period	4 years
RSUs
Significant Accounting Policies [Line Items]
Vesting period	4 years
RSUs | Share-based Payment Arrangement, Tranche One
Significant Accounting Policies [Line Items]
Vesting period	1 year
Vesting percentage	25.00%
RSUs | Share-based Payment Arrangement, Tranche Two
Significant Accounting Policies [Line Items]
Vesting period	3 years
Maximum
Significant Accounting Policies [Line Items]
Definite lived intangible assets, estimated useful life	12 years
Computer equipment
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
Land Improvements
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives	15 years
Buildings
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful lives	40 years
ASU 2016-02
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets					565
Operating lease, liability					615
Effect of retained earnings					$ 6
Deferred Merchant Bookings
Significant Accounting Policies [Line Items]
Deferred merchant bookings liability, current	$ 4,898	$ 3,627
Deferred merchant booking liability, decrease due to recognition during period	3,309
Contract with customer, liability, revenue recognized	488
Deferred Loyalty Rewards
Significant Accounting Policies [Line Items]
Deferred merchant bookings liability, current	$ 781	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	$ 326
Deferred revenue	$ 321	$ 364