Unbilled Trade Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 91,355	$ 135,029
Allowance for sales credit memos	(772)	(963)
Total accounts receivable net	90,583	134,066
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	58,037	112,106
Unbilled trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 33,318	$ 22,923