Commitments and Contingencies - Litigation (Details) $ in Millions			1 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) lawsuit item	Aug. 01, 2015	Sep. 30, 2015 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2017 USD ($) lawsuit item	Dec. 31, 2016 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2009 USD ($)
Expedia | Occupancy Tax Litigation
Loss Contingencies [Line Items]
Number of lawsuits filed by cities, counties and states involving hotel occupancy taxes | lawsuit	95				95
Number of lawsuits currently active | lawsuit	17				17
Number of lawsuits dismissed to date | lawsuit	41
Number of dismissals based on finding that defendant was not subject to local hotel occupancy tax or the local government lacked standing to pursue claims | item	27
Loss contingency reserve	$ 40.0				$ 40.0
Loss contingency estimated loss	23.0				$ 23.0
Expedia | Hawaii General Excise Tax Litigation
Loss Contingencies [Line Items]
Proceeds from tax refund			$ 132.0
Tax paid, net of refunds							$ 171.0
Expected Occupancy And Other Tax Assessment Payments	$ 16.7
Expedia | San Francisco Occupancy Tax Litigation [member]
Loss Contingencies [Line Items]
Occupancy And Other Tax Assessment Payments				$ 25.5				$ 48.0
Expedia | Competition Reviews And Legislation Relating To Parity Clauses
Loss Contingencies [Line Items]
Period when certain parity clauses were waived		5 years
Number of Italian hotel trade associations appealing the case closure | item	2				2
Number of NCA's in working group to monitor online hotel bookings | item	10				10
Orbitz Worldwide Inc | Hawaii General Excise Tax Litigation
Loss Contingencies [Line Items]
Proceeds from tax refund			$ 22.0
Orbitz Worldwide Inc | San Francisco Occupancy Tax Litigation [member]
Loss Contingencies [Line Items]
Occupancy And Other Tax Assessment Payments					$ 4.6
Expedia and Orbitz [member] | Hawaii General Excise Tax Litigation
Loss Contingencies [Line Items]
Tax paid, net of refunds						$ 44.0