Stock-Based Compensation Plans - Schedule of Weighted-Average Assumptions Used for Grants Made Under Stock Option Plans (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Directors [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected volatility, Minimum	147.57%	143.09%	138.29%
Expected volatility, Maximum	148.95%	145.11%	141.54%
Expected term	6 years 9 months 18 days	6 years 9 months 18 days	6 years 9 months 18 days
Risk-free interest rate, Minimum	1.83%	1.97%	1.45%
Risk-free interest rate, Maximum	1.93%	2.20%	2.24%
Dividend yield	0.00%	0.00%	0.00%
Annual forfeiture rate	14.50%	14.50%	14.50%
Executives [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected volatility, Minimum	145.87%
Expected volatility, Maximum	148.05%
Expected volatility		142.69%	134.90%
Expected term	6 years 9 months 15 days	6 years 9 months 18 days	6 years 9 months 18 days
Risk-free interest rate, Minimum	1.58%
Risk-free interest rate, Maximum	1.90%
Risk-free interest rate		2.22%	1.21%
Dividend yield	0.00%	0.00%	0.00%
Annual forfeiture rate	14.50%	14.50%	14.50%
Employees [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected volatility, Minimum			134.90%
Expected volatility, Maximum			141.98%
Expected volatility	148.06%	145.03%
Expected term	6 years 9 months 18 days	6 years 9 months 18 days	6 years 9 months 18 days
Risk-free interest rate, Minimum			1.21%
Risk-free interest rate, Maximum			2.03%
Risk-free interest rate	1.99%	1.75%
Dividend yield	0.00%	0.00%	0.00%
Annual forfeiture rate	14.50%	14.50%	14.50%