Property and Equipment, net - Detail of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 373,774	$ 345,490
Less: accumulated amortization and depreciation	(185,742)	(175,001)
Property and equipment, net	188,032	170,489
Website development costs
Property, Plant and Equipment [Line Items]
Property and equipment	153,201	149,648
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	101,970	81,981
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property and equipment	46,442	45,337
Office equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	40,612	36,582
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 31,549	$ 31,942