Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands						2 Months Ended	12 Months Ended
	Feb. 09, 2016	Jul. 10, 2015	Jun. 11, 2015	Feb. 20, 2015	Apr. 30, 2014	Mar. 03, 2016	Mar. 03, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Mar. 30, 2014	Dec. 31, 2012
Subsequent Event [Line Items]
Net Proceeds		$ 5,800	$ 46,400		$ 52,400			$ 58,331	$ 52,433
Total shares of common stock sold								100,180,872	63,182,806	48,855,255	244,276,923	5,391,095
Cantor Fitzgerald & Co. [Member]
Subsequent Event [Line Items]
Average price per share								$ 3.25
Gross proceeds								$ 6,546
Sale of common stock in an at-the-market offering				25,000,000
Percentage of commission paid				3.00%
Cantor Fitzgerald & Co. [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Total shares of common stock sold						5,710,214
Average price per share						$ 3.23
Gross proceeds						$ 18,400	$ 25,000
Net Proceeds						$ 17,900	$ 24,000
Total shares of common stock sold						7,724,488	7,724,488
Sale of common stock in an at-the-market offering	43,560,000
Percentage of commission paid	3.00%