Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
(Loss) income before income tax (benefit) expense	$ (2,185)	$ 11,559	$ 22,971
Income taxes computed at the Federal statutory rate	(459)	4,046	8,040
State income taxes, net of Federal benefit	306	472	867
Impact of 2017 Tax Act	0	24,235	0
Research and development and other tax credits	(1,144)	(1,775)	0
Excess executive compensation	281	0	0
Other	310	(113)	85
Income tax (benefit) expense	$ (706)	$ 26,865	$ 8,992
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Income taxes computed at the Federal statutory rate	21.00%	35.00%	35.00%
State income taxes, net of Federal benefit	(14.00%)	4.10%	3.80%
Impact of 2017 Tax Act	0.00%	209.70%	0.00%
Research and development and other tax credits	52.40%	(15.40%)	(0.00%)
Excess executive compensation	(12.90%)	0.00%	0.00%
Other	(14.20%)	(1.00%)	0.40%
Income tax (benefit) expense	32.30%	232.40%	39.10%