Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Contingency [Line Items]
Unrecognized tax benefit, beginning of year	$ 56,170	$ 37,428	$ 40,900
Tax positions related to current year		38,329
Tax positions related to prior years	38,329	(19,587)	37,427
Settlements			(3,089)
Statute expirations	(38,329)		(37,810)
Unrecognized tax benefit, end of year	$ 56,170	$ 56,170	$ 37,428