Trade Receivables of Major Customers (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2012 Customer A	Dec. 31, 2012 Customer B
Revenue from External Customer [Line Items]
Total Revenue	$ 116,246	$ 111,167
Major customer percentage of total revenue				11.00%
Trade receivables, net of allowances	$ 70,513		$ 134,066
Major customer percentage of trade receivables					10.00%