General - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	May 31, 2018
Debt Instrument [Line Items]
Cash and cash equivalents	$ 72,945		$ 72,945				$ 7,703
Cash and cash equivalents	72,945		72,945				$ 7,703
Marketable securities	$ 25,000		$ 25,000
Discount rate	12.00%		12.00%
Operating lease, payments	$ 100	$ 100	$ 200	$ 300
Payments to be received	3,658		3,658		$ 3,700
Operating lease, liability	2,965		2,965
Revolving Credit Facility
Debt Instrument [Line Items]
Cash and cash equivalent threshold								$ 50,000
Amended Credit Facility
Debt Instrument [Line Items]
Long-term line of credit outstanding	44,500		44,500
Cash and cash equivalent threshold	$ 50,000		$ 50,000					$ 50,000
Accounting Standards Update 2016-02
Debt Instrument [Line Items]
Right-of-use asset						$ 2,200
Operating lease, liability						2,900
Deferred rent credit						$ 700