Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

Name:	us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.

Subsequent Events (Details) - USD ($)			6 Months Ended
Subsequent Events (Details) - USD ($)	Jul. 24, 2015	Feb. 05, 2014	Jun. 30, 2015	Jun. 30, 2014	Jul. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Stock issued, underwritten public offering, value		$ 86,000,000
Stock issued underwritten public offering (in shares)		13,200,000
Share price (in dollars per share)		$ 6.50
Proceeds, exclusive of treasury shares			$ 0	$ 80,535,401
Current assets:
Cash and cash equivalents			38,833,736	$ 51,866,891		$ 32,218,905	$ 11,483,112
Short-term investments			15,002,213			45,621,593
Prepaid and other current assets			976,325			3,250,355
Total current assets			60,001,477			83,214,773
Total assets			62,633,809			85,692,582
LIABILITIES AND STOCKHOLDERS' EQUITY
Warrant liability			4,566,515		$ 0	5,131,085
Total current liabilities			20,271,281			17,781,119
Stockholders' equity
Common stock			55,927			55,924
Additional paid-in capital			380,638,689			376,975,984
Treasury stock			(2,612,861)			(2,612,861)
Accumulated deficit			(335,719,227)			(306,507,584)
Total stockholders' equity			42,362,528			67,911,463
Total liabilities and stockholders' equity			62,633,809			85,692,582
Warrant liability			4,566,515		0	$ 5,131,085
Actual [Member]
Current assets:
Cash and cash equivalents			38,833,736
Short-term investments			15,002,213
Prepaid and other current assets			6,165,528
Total current assets			60,001,477
Non-current assets			2,632,332
Total assets			62,633,809
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable and other current liabilities			15,704,766
Total current liabilities			20,271,281
Stockholders' equity
Common stock			55,927
Additional paid-in capital			380,638,689
Treasury stock			(2,612,861)
Accumulated deficit			(335,719,227)
Total stockholders' equity			42,362,528
Total liabilities and stockholders' equity			62,633,809
Pro Forma [Member]
Current assets:
Cash and cash equivalents			65,585,761
Short-term investments			15,002,213
Prepaid and other current assets			6,431,491
Total current assets			87,019,465
Non-current assets			2,632,332
Total assets			89,651,797
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable and other current liabilities			15,704,766
Total current liabilities			20,271,281
Stockholders' equity
Common stock			66,392
Additional paid-in capital			407,380,249
Treasury stock			(2,612,861)
Accumulated deficit			(335,719,227)
Total stockholders' equity			69,114,553
Total liabilities and stockholders' equity			$ 89,385,834
Subsequent Event [Member] \| IPO [Member]
Subsequent Event [Line Items]
Stock issued, underwritten public offering, value	$ 28,700,000
Stock issued underwritten public offering (in shares)	10,465,000
Share price (in dollars per share)	$ 2.75
Proceeds, exclusive of treasury shares	$ 26,800,000
Subsequent Event [Member] \| Adjustment [Member]
Current assets:
Cash and cash equivalents					26,752,025
Short-term investments					0
Prepaid and other current assets					0
Total current assets					26,752,025
Non-current assets					0
Total assets					26,752,025
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable and other current liabilities					0
Total current liabilities					0
Stockholders' equity
Common stock					10,465
Additional paid-in capital					26,741,560
Treasury stock					0
Accumulated deficit					0
Total stockholders' equity					26,752,025
Total liabilities and stockholders' equity					$ 26,752,025