Contractual Obligations, Including Capital Expenditures and Future Minimum Lease Payments Under Non-Cancelable Operating Lease Arrangements and Purchase Commitments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long-term Purchase Commitment [Line Items]
Rental expense on lease	$ 819	$ 618	$ 661