Liquidity (Details) (USD $)	3 Months Ended								12 Months Ended			0 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 13, 2014 Private Placement [Member]
liquidity And Working Capital [Line Items]
Net loss	$ (7,859,000)	$ (6,424,000)	$ (7,127,000)	$ (6,462,000)	$ (6,174,000)	$ (5,019,000)	$ (5,061,000)	$ (4,068,000)	$ (27,872,293)	$ (20,321,812)	$ (14,573,353)
Net cash used in operating activities									(18,861,413)	(14,663,683)	(11,436,547)
Accumulated deficit	(290,010,708)				(262,138,415)				(290,010,708)	(262,138,415)
Net working capital	15,200,000								15,200,000
Cash, cash equivalents, and available for sale securities	17,200,000								17,200,000
Proceeds from issurance of common stock in private placement												$ 11,900,000