Common Stock Option and Restricted Stock Award Activity (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Options Granted	7,167,585
Number Of Shares, Options Forfeited	(424,170)
Number of Shares, Total vested shares (options)	4,509,238
Weighted Average Exercise Price Per share, End of year	$ 1.46
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Beginning of year	689,529
Shares Available For Grant, Options Granted	(1,908,661)
Shares Available For Grant, Options Forfeited	53,021
Shares Available For Grant, Options Expired	42,417
Shares Available For Grant, Options canceled	1,432,661
Shares Available For Grant, Restricted Stock Granted	(34,958)
Shares Available For Grant, Restricted Stock Vested	0
Shares Available for Grant, End of year	274,009
Number of Shares, Beginning of Year	2,417,918
Number of Shares, Options Granted	1,908,661
Number Of Shares, Options Forfeited	(53,021)
Number Of Shares, Options Expired	(42,417)
Number Of Shares, Options canceled	(1,432,661)
Number of Shares, Restricted Stock Granted	34,958
Number of Shares, Restricted Stock Vested	(34,958)
Number of Shares, End of Year	2,798,480
Number of Shares, Total vested and expected to vest shares (options)	2,798,480
Number of Shares, Total vested shares (options)	739,819
Weighted Average Exercise Price Per share, Beginning of year	$ 2.59
Weighted Average Exercise Price Per Share, Options Granted	$ 1.02
Weighted Average Exercise Price Per Share, Options Forfeited	$ 2.27
Weighted Average Exercise Price Per Share, Options Expired	$ 2.27
Weighted Average Exercise Price Per Share, Options canceled	$ 2.73
Weighted Average Exercise Price Per Share, Restricted Stock Granted	$ 0.76
Weighted Average Exercise Price Per Share, Restricted Stock Vested	$ 0.76
Weighted Average Exercise Price Per share, End of year	$ 1.46
Weighted Average Exercise Price Per Share, Total vested and expected to vest shares (options)	$ 1.46
Weighted Average Exercise Price Per Share, Total vested shares (options)	$ 2.72