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Income Taxes - Additional Information (Detail) (USD $) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Income Taxes Disclosure [Line Items] |  |  |
Provision for federal or state income taxes |  | $ 0 | $ 0
Net Operating Loss Carryforwards expiration start year | 2023 |  |
Net Operating Loss Carryforwards expiration ending year | 2030 |  |
Federal Tax credit expiration start year | 2020 |  |
Federal Tax credit expiration ending year | 2032 |  |
Net operating loss |  | 10,600,000 |
Net operating losses limited for year minimum |  | 2013 |
Net operating losses limited for year maximum |  | 2027 |
Remaining portion of net operating losses |  | 90,300,000 |
Gross unrecognized tax benefits |  | 1,140,067 | 1,105,256
Unrecognized interest or penalties |  | 0 | 0
Income tax examination year subject to examination, Range start | 2001 |  |
Income tax examination year subject to examination, Range End | 2012 |  |
Minimum [Member] |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating losses limited for use utilized on an annual basis |  | 200,000 |
Maximum [Member] |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating losses limited for use utilized on an annual basis |  | 2,100,000 |
U.S. Federal Government [Member] |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | 100,900,000 |  |
Tax credit carryforwards | 21,800,000 |  |
State and Local Jurisdiction [Member] |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | 64,200,000 |  |
Immaterial error related to net operating loss carryforwards | $ 1,200,000 |  |

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