Schedule of Total Revenue from Major Customers (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Major Customer A
Revenue, Major Customer [Line Items]
Percentage of total revenue	13.70%	15.00%	15.00%
Major Customer B
Revenue, Major Customer [Line Items]
Percentage of total revenue	35.20%	33.30%	37.50%