Common Stock Option and Restricted Stock Award Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options assumed in Merger	15,000
Number of Shares, Total vested shares (options)	4,509,238
Weighted Average Exercise Price Per Share, Options assumed in Merger	$ 14.30
Weighted Average Exercise Price Per share, End of year	$ 2.59
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Beginning of year		1,286,647
Shares Available For Grant, Authorized	706,950
Shares Available For Grant, Options Granted	(1,109,198)
Shares Available For Grant, Options assumed in Merger	0
Shares Available For Grant, Restricted Stock Granted	(194,870)
Shares Available For Grant, Restricted Stock Vested	0
Shares Available for Grant, End of year	689,529	1,286,647
Number of Shares, Beginning of Year		1,611,848
Number of Shares, Authorized	0
Number of Shares, Options Granted	1,109,198
Number of Shares, Options assumed in Merger	15,000
Number of Shares, Restricted Stock Granted	194,870
Number of Shares, Restricted Stock Vested	(512,998)
Number of Shares, End of Year	2,417,918	1,611,848
Number of Shares, Total vested and expected to vest shares (options)	2,417,918
Number of Shares, Total vested shares (options)	676,275
Weighted Average Exercise Price Per share, Beginning of year		$ 2.27
Weighted Average Exercise Price Per Share, Authorized	$ 0
Weighted Average Exercise Price Per Share, Options Granted	$ 2.80
Weighted Average Exercise Price Per Share, Restricted Stock Granted	$ 1.45
Weighted Average Exercise Price Per Share, Restricted Stock Vested	$ 1.96
Weighted Average Exercise Price Per share, End of year	$ 2.59	$ 2.27
Weighted Average Exercise Price Per Share, Total vested and expected to vest shares (options)	$ 2.59
Weighted Average Exercise Price Per Share, Total vested shares (options)	$ 2.77