Property and Equipment, net - Detail of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 390,126	$ 345,490
Less: accumulated amortization and depreciation	(194,379)	(175,001)
Property and equipment, net	195,747	170,489
Website development costs
Property, Plant and Equipment [Line Items]
Property and equipment	157,468	149,648
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	107,139	81,981
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment	51,482	45,337
Office equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	42,236	36,582
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 31,801	$ 31,942