Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Loss Contingencies [Line Items]
Accrual for the probable payment of pending claims	$ 16,861,000
Operating leases rent expenses	9,184,000	5,553,000	4,999,000
Total future minimum lease obligation	$ 7,253,000
Future minimum lease obligation payment period	6 years