Income Taxes - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Income Tax Disclosure [Line Items]
Total current and long term deferred tax assets	$ 19,800,000
Research and development tax credit studies	7,800,000
Liability for unrecognized tax benefits	3,074,447	2,902,896
Effective tax rate, before discrete period adjustments	32.20%
Anticipated annual income tax rate	38.20%
Federal [Member]
Income Tax Disclosure [Line Items]
Liability for unrecognized tax benefits	2,900,000
State [Member]
Income Tax Disclosure [Line Items]
Liability for unrecognized tax benefits	$ 200,000