Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 12,837	$ 10,499
Less accumulated depreciation and amortization	(6,803)	(5,849)
Property and equipment, net	6,034	4,650
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,689	1,189
Property and equipment, useful life in years	5 years
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 3,958	2,776
Property and equipment, useful life in years	5 years
Systems Hardware
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,476	1,404
Property and equipment, useful life in years	5 years
Office Computers
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 4,306	3,745
Property and equipment, useful life in years	3 years
Computer and System Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,408	$ 1,385
Property and equipment, useful life in years	3 years