Unbilled Trade Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 135,029	$ 99,219
Allowance for doubtful accounts		(31)
Allowance for sales credit memos	(963)	(895)
Total allowance	(963)	(926)
Total accounts receivable net	134,066	98,293
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	112,106	77,123
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 22,923	$ 22,096