Property and Equipment - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 20,384	$ 17,670
Less accumulated depreciation	(14,940)	(13,280)
Property and equipment, net	5,444	4,390
Depreciation expense	$ 1,700	1,200	$ 900
Leasehold Improvements
Property Plant And Equipment [Line Items]
Depreciable life	Shorter of estimated useful life or life of lease
Property and equipment, gross	$ 3,327	3,278
Office furniture, fixtures and equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 17,057	$ 14,392
Office furniture, fixtures and equipment | Minimum
Property Plant And Equipment [Line Items]
Depreciable life	2 years
Office furniture, fixtures and equipment | Maximum
Property Plant And Equipment [Line Items]
Depreciable life	10 years