Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (45,254)	$ (41,614)
Property and equipment, net	47,649	43,988
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	31,132	29,558
Website and software development costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 35,308	33,278
Website and software development costs \| Minimum
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	2 years
Website and software development costs \| Maximum
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Computer and office equipment
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Property and equipment, gross	$ 9,922	7,765
Software
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Property and equipment, gross	$ 1,871	1,858
Furniture
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	7 years
Property and equipment, gross	$ 7,277	7,450
Property and equipment, gross
Property, Plant and Equipment [Line Items]
Property and equipment, gross	85,510	79,909
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,393	$ 5,693

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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