Nature of Business and Summary of Significant Accounting Policies - Black Scholes Options-Pricing Model, Assumptions (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Dividend yield
Minimum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expected price volatility	77.59%	81.96%	69.05%
Risk-free interest rate	0.70%	0.62%	0.90%
Weighted average expected life in years	5 years	5 years	5 years
Maximum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Expected price volatility	81.65%	83.69%	77.75%
Risk-free interest rate	1.60%	1.02%	1.99%
Weighted average expected life in years	6 years	6 years	6 years