Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property Plant and Equipment [Line Items]
Property and equipment at cost	$ 85,366	$ 74,859
Less: Accumulated depreciation	(33,111)	(26,120)
Property and equipment, net	52,255	48,739
Land
Property Plant and Equipment [Line Items]
Property and equipment at cost	1,240	972
Equipment
Property Plant and Equipment [Line Items]
Property and equipment at cost	15,437	12,171
Furniture, fixtures, and leasehold improvements
Property Plant and Equipment [Line Items]
Property and equipment at cost	20,892	21,280
Computer hardware, software, and phone equipment
Property Plant and Equipment [Line Items]
Property and equipment at cost	11,566	9,571
Buildings
Property Plant and Equipment [Line Items]
Property and equipment at cost	8,145	2,559
Deemed assets from landlord building construction
Property Plant and Equipment [Line Items]
Property and equipment at cost	22,752	22,752
Construction-in-Progress
Property Plant and Equipment [Line Items]
Property and equipment at cost	$ 5,334	$ 5,554