Commitments and Contingencies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2014
Line of Credit Facility [Line Items]
Rent deposits	$ 600,000	$ 400,000
Deferred rent liability	300,000	300,000
Loss contingency, liability			$ 420,000
Revolving credit facility | Line of credit
Line of Credit Facility [Line Items]
Revolving line of credit, borrowing capacity	$ 40,000,000.0
Unused credit fee (percent)	0.20%
Outstanding	$ 0	0
Available borrowing capacity	40,000,000	40,000,000
Letter of credit | Line of credit
Line of Credit Facility [Line Items]
Outstanding	$ 0	$ 0