Debt - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Apr. 30, 2008
Debt Instrument [Line Items]
Bank loan			$ 19,200,000
Borrowing repayment period	5 years
Interest rate	4.96%
Total outstanding debt		4,000,000
Outstanding debt due with in twelve months		$ 2,978,000