Summary of Depreciation Expense on Property Plant and Equipment and Accumulated Amortization of Capital Leases (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Depreciation and Other Amortization Expenses [Line Items]
Depreciation expense	$ 9,612	$ 7,100	$ 6,393
Accumulated amortization on capital lease	$ 861	$ 123