Acquired Intangible Assets, Net - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets	$ 2,028,498	$ 2,186,203	$ 2,011,639
Estimated amortization expense on intangible assets, next twelve months	2,000,000
Estimated amortization expense on intangible assets, year two	2,000,000
Estimated amortization expense on intangible assets, year three	2,000,000
Estimated amortization expense on intangible assets, year four	2,000,000
Estimated amortization expense on intangible assets, year five	$ 2,000,000