11. Commitments and contingencies (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Leases, Rent Expense	$ 1,005,000	$ 1,030,000	$ 1,047,000
Operating Leases, Future Minimum Payments Due, Current	836,000
Operating Leases, Future Minimum Payments, Due in Two Years	806,000
Operating Leases, Future Minimum Payments, Due in Three Years	808,000
Operating Leases, Future Minimum Payments, Due in Four Years	561,000
Operating Leases, Future Minimum Payments, Due in Five Years	$ 78,000