Income Taxes - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Income Tax Disclosure [Line Items]
Total current and long term deferred tax assets	$ 21,100,000
Research and development tax credit studies	7,900,000
Liability for unrecognized tax benefits	3,072,863	2,902,896
Effective tax rate, before discrete period adjustments	35.70%
Anticipated annual income tax rate	38.80%
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