Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2017

Equity [Abstract]

Schedule of weighted-average valuation assumptions

	Three Months Ended March 31,
	2016		2017
Expected volatility	99.37	%	93.02	%
Risk-free interest rate	1.46	%	2.12	%
Weighted-average expected life (in years)	6.3		6.3
Dividend yield	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, 2017	6,447,594	$	6.41
Granted during period	653,842		2.17
Exercised during period	(7,757)		2.10
Expired during period	(163,836)		8.82
Forfeited during period	(68,875)		5.59
Outstanding at March 31, 2017	6,860,968	$	5.96	6.27	$	282,786
Exercisable at March 31, 2017	5,085,833	$	6.72	5.33	$	29,895

Schedule of restricted stock unit activity

	Restricted	Weighted-Average
	Stock	Grant
	Units	Date Fair Value
Outstanding at January 1, 2017	394,132	$	4.96
Granted during period	367,985		2.17
Vested during period	(128,225)		5.77
Forfeited during period	(16,980)		3.50
Outstanding at March 31, 2017	616,912	$	3.17