Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Schedule of weighted-average valuation assumptions

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2018		2017		2018
Expected volatility	0.0	%	90.6	%	92.7	%	100.4	%
Risk-free interest rate	0.00	%	2.78	%	2.15	%	2.71	%
Weighted-average expected life (in years)	0.0		6.3		6.9		6.9
Dividend yield	0.00	%	0.00	%	0.00	%	0.00	%

Schedule of stock option activity

				Weighted-Average
				Remaining
		Weighted-Average		Contractual Term	Aggregate
	Options	Exercise Price		(In Years)	Intrinsic Value
Outstanding at January 1, 2018	5,878,660	$	5.93
Granted during period	688,192		3.07
Exercised during period	(561,088)		4.10
Expired during period	(8,993)		3.06
Outstanding at March 31, 2018	5,996,771	$	5.78	6.18	$	22,125,418
Exercisable at March 31, 2018	4,290,445	$	6.92	5.02	$	11,551,954
Outstanding at April 1, 2018	5,996,771		5.78
Granted during period	242,400		10.86
Exercised during period	(512,795)		8.16
Forfeited during period	(5,869)		2.82
Outstanding at June 30, 2018	5,720,507	$	5.79	6.28	$	45,908,925
Exercisable at June 30, 2018	3,970,287	$	6.56	5.09	$	28,812,888
Outstanding at July 1, 2018	5,720,507		5.79
Granted during period	48,700		16.74
Exercised during period	(442,913)		7.57
Forfeited during period	(16,950)		4.77
Outstanding at September 30, 2018	5,309,344	$	5.74	6.14	$	63,541,222
Exercisable at September 30, 2018	3,550,137	$	6.42	4.84	$	40,064,166

Schedule of restricted stock unit activity

	Restricted	Weighted-Average
	Stock	Grant
	Units	Date Fair Value
Outstanding at January 1, 2018	1,383,770	$	5.05
Granted during period	301,958		3.02
Vested during period	(161,147)		4.27
Outstanding at March 31, 2018	1,524,581	$	4.73
Outstanding at April 1, 2018	1,524,581	$	4.73
Granted during period	56,150		12.19
Vested during period	(30,150)		2.47
Forfeited during period	(29,683)		5.35
Outstanding at June 30, 2018	1,520,898	$	5.04
Outstanding at July 1, 2018	1,520,898	$	5.04
Granted during period	3,000		13.60
Vested during period	(5,938)		4.85
Forfeited during period	(7,500)		5.01
Outstanding at September 30, 2018	1,510,460	$	5.06