Subsequent Event (Details) - USD ($)	1 Months Ended		3 Months Ended
	Apr. 30, 2016	Oct. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	May. 31, 2015
Subsequent Event [Line Items]
Shares sold in follow-on public offering		6,272,727	499,000
Public price (in usd per share)		$ 5.50
Shelf registration, maximum aggregate offering price		$ 165,500,000	$ 161,000,000		$ 200.0
At-the-market sales agreement, maximum common stock shares authorized value		75,000,000	70,500,000		$ 75,000,000
Proceeds from issuance of common stock, net of issuance costs		32,100,000	4,325,000	$ 0
Underwriting discounts and commissions		2,100,000	134,000
Estimated offering expenses		$ 280,000	$ 75,000
Weighted Average [Member]
Subsequent Event [Line Items]
Public price (in usd per share)			$ 8.95
Subsequent Event [Member]
Subsequent Event [Line Items]
Shares sold in follow-on public offering	264,234
Shelf registration, maximum aggregate offering price	$ 158,600,000.0
At-the-market sales agreement, maximum common stock shares authorized value	68,100,000.0
Proceeds from issuance of common stock, net of issuance costs	2,300,000
Underwriting discounts and commissions	73,000
Estimated offering expenses	$ 45,000
Subsequent Event [Member] | Weighted Average [Member]
Subsequent Event [Line Items]
Public price (in usd per share)	$ 9.17