Restatement of Unaudited Interim Consolidated Financial Statements - Adjustment to Financial Statements (Detail) (USD $)	3 Months Ended								9 Months Ended	12 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	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common stock warrant liability	$ 379,468	$ 696,065			$ 1,173,747				$ 696,065	$ 379,468	$ 1,173,747
Total liabilities	12,664,838	13,307,995			4,953,207				13,307,995	12,664,838	4,953,207
Accumulated deficit	(241,661,706)	(242,748,816)			(248,365,480)				(242,748,816)	(241,661,706)	(248,365,480)
Total shareholders' equity	46,877,622	45,922,701			31,365,457				45,922,701	46,877,622	31,365,457
Change in fair value of common stock warrants		427,656							477,682	(794,280)	(6,995,099)	2,164,543
(Loss) income before income taxes		1,720,767							5,624,838	6,726,338	9,919,980	20,566,474
Net (loss) income	1,087,112	1,718,143	2,656,879	1,241,640	2,631,341	388,729	1,942,810	4,954,393	5,616,664	6,703,774	9,917,273	20,527,192
Basic net (loss) income per common share	$ 0.09	$ 0.15	$ 0.24	$ 0.11	$ 0.24	$ 0.04	$ 0.18	$ 0.45	$ 0.51	$ 0.59	$ 0.91	$ 1.90
Diluted net (loss) income per common share	$ 0.06	$ 0.11	$ 0.24	$ 0.09	$ 0.09	$ 0.04	$ 0.16	$ (0.12)	$ 0.46	$ 0.52	$ 0.26	$ 1.73
Basic weighted average common shares outstanding		11,137,780							10,994,382	11,259,347	10,914,476	10,790,669
Diluted weighted average common shares outstanding		11,293,029							11,148,275	11,273,456	11,063,034	11,568,644
Net (loss) income	1,087,112	1,718,143	2,656,879	1,241,640	2,631,341	388,729	1,942,810	4,954,393	5,616,664	6,703,774	9,917,273	20,527,192
Comprehensive (loss) income		2,355,853							6,155,222	7,790,424	10,095,592	20,435,490
Net income	1,087,112	1,718,143	2,656,879	1,241,640	2,631,341	388,729	1,942,810	4,954,393	5,616,664	6,703,774	9,917,273	20,527,192
Change in fair value of common stock warrants									(477,682)	(794,280)	(6,995,099)	2,164,543
As Previously Reported [Member]
Common stock warrant liability		5,568,525							5,568,525
Total liabilities		18,180,455							18,180,455
Accumulated deficit		(247,621,276)							(247,621,276)
Total shareholders' equity		41,050,241							41,050,241
Change in fair value of common stock warrants		(4,444,804)							(4,394,778)
(Loss) income before income taxes		(3,151,693)							752,378
Net (loss) income		(3,154,317)							744,204
Basic net (loss) income per common share		$ (0.28)							$ 0.07
Diluted net (loss) income per common share		$ (0.28)							$ 0.07
Basic weighted average common shares outstanding		11,137,780							10,994,382
Diluted weighted average common shares outstanding		11,137,780							11,148,275
Net (loss) income		(3,154,317)							744,204
Comprehensive (loss) income		(2,516,607)							1,282,762
Net income		(3,154,317)							744,204
Change in fair value of common stock warrants									4,394,778
Adjustment [Member]
Common stock warrant liability		(4,872,460)							(4,872,460)
Total liabilities		(4,872,460)							(4,872,460)
Accumulated deficit		4,872,460							4,872,460
Total shareholders' equity		4,872,460							4,872,460
Change in fair value of common stock warrants		4,872,460							4,872,460
(Loss) income before income taxes		4,872,460							4,872,460
Net (loss) income		4,872,460							4,872,460
Basic net (loss) income per common share		$ 0.43							$ 0.44
Diluted net (loss) income per common share		$ 0.39							$ 0.39
Diluted weighted average common shares outstanding		155,249
Net (loss) income		4,872,460							4,872,460
Comprehensive (loss) income		4,872,460							4,872,460
Net income		4,872,460							4,872,460
Change in fair value of common stock warrants									$ (4,872,460)