Consolidated Statements of Stockholders Equity (Deficit) - USD ($) $ in Thousands	Common Stock Class A	Common Stock Class B	Additional Paid-In Capital	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Deficit	Cumulative Effect, Period of Adoption, Adjustment [Member]	Total
Beginning balance at Dec. 31, 2018	$ 1	$ 1	$ 590,538	$ 340	$ (471,238)	$ 340	$ 119,302
Beginning balance (in shares) at Dec. 31, 2018	5,240,073	7,714,036
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	1,104,091	(1,104,091)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0	$ 0	103				103
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	23,911	27,444
Share-based compensation			2,974				2,974
Net income (loss)					(5,275)		(5,275)
Ending balance at Mar. 31, 2019	$ 1	$ 1	593,615		(476,173)		117,444
Ending balance (in shares) at Mar. 31, 2019	6,368,075	6,637,389
Beginning balance at Dec. 31, 2018	$ 1	$ 1	590,538	$ 340	(471,238)	$ 340	119,302
Beginning balance (in shares) at Dec. 31, 2018	5,240,073	7,714,036
Net income (loss)							(39,219)
Ending balance at Sep. 30, 2019	$ 1	$ 1	597,603		(510,117)		87,488
Ending balance (in shares) at Sep. 30, 2019	7,608,045	5,564,196
Beginning balance at Mar. 31, 2019	$ 1	$ 1	593,615		(476,173)		117,444
Beginning balance (in shares) at Mar. 31, 2019	6,368,075	6,637,389
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	210,664	(210,664)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0	$ 0	(9)				(9)
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	80,391	139
Share-based compensation			1,724				1,724
Other	$ 0	$ 0
Other (in shares)	(64)	(35)
Net income (loss)					(7,748)		(7,748)
Ending balance at Jun. 30, 2019	$ 1	$ 1	595,330		(483,921)		111,411
Ending balance (in shares) at Jun. 30, 2019	6,659,066	6,426,829
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	862,633	(862,633)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0		(38)				(38)
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	86,346
Share-based compensation			2,311				2,311
Net income (loss)					(26,196)		(26,196)
Ending balance at Sep. 30, 2019	$ 1	$ 1	597,603		(510,117)		87,488
Ending balance (in shares) at Sep. 30, 2019	7,608,045	5,564,196
Beginning balance at Dec. 31, 2019	$ 1	$ 1	599,976		(531,979)		67,999
Beginning balance (in shares) at Dec. 31, 2019	7,799,093	5,464,196
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	1,835,947	(1,835,947)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0	$ 0	486				486
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	92,243	25,999
Share-based compensation			2,321				2,321
Net income (loss)					(20,145)		(20,145)
Ending balance at Mar. 31, 2020	$ 1	$ 1	602,783		(552,124)		50,661
Ending balance (in shares) at Mar. 31, 2020	9,727,283	3,654,248
Beginning balance at Dec. 31, 2019	$ 1	$ 1	599,976		(531,979)		67,999
Beginning balance (in shares) at Dec. 31, 2019	7,799,093	5,464,196
Net income (loss)							(34,293)
Ending balance at Sep. 30, 2020	$ 1	$ 1	639,918		(566,272)		73,648
Ending balance (in shares) at Sep. 30, 2020	14,031,986	3,653,820
Beginning balance at Mar. 31, 2020	$ 1	$ 1	602,783		(552,124)		50,661
Beginning balance (in shares) at Mar. 31, 2020	9,727,283	3,654,248
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	101	(101)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0		(3)				(3)
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	159,260
Share-based compensation			2,097				2,097
Net income (loss)					1,114		1,114
Ending balance at Jun. 30, 2020	$ 1	$ 1	604,877		(551,010)		53,869
Ending balance (in shares) at Jun. 30, 2020	9,886,644	3,654,147
Conversion from Class B to Class A common stock	$ 0	$ 0
Conversion from Class B to Class A common stock (in shares)	327	(327)
Issuance of common stock upon exercise of stock options and vesting of restricted stock, net of tax withholdings	$ 0		(7)				(7)
Issuance of common stock upon exercise of stock options and vesting of restricted stock (in shares)	145,015
Issuance of common stock, net of offering costs	$ 0		32,867				32,867
Issuance of stock (in shares)	4,000,000
Share-based compensation			2,181				2,181
Net income (loss)					(15,262)		(15,262)
Ending balance at Sep. 30, 2020	$ 1	$ 1	$ 639,918		$ (566,272)		$ 73,648
Ending balance (in shares) at Sep. 30, 2020	14,031,986	3,653,820