Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Summary Of Net Deferred Tax Assets [Line Items]
Valuation allowance against net deferred tax assets	$ 24.5	$ 23.9
Percentage of ownership change, limitations on utilization of net operating loss (NOL) and research and development (R&D) credit carryforwards	50.00%
Ownership change test period, limitations on utilization of net operating loss (NOL) and research and development (R&D) credit carryforwards	3 years
Net federal operating loss	53.0
Future annual deductibility of company's total net operating loss carryforwards	$ 2.5
Description of net operating losses	The Company believes limitations exist only on the future annual deductibility of approximately $0.0 million of the Company's total net operating loss carryforwards