Schedule of Trade Accounts Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 269,154	$ 216,477
Allowance for sales credit memos	(4,126)	(4,631)
Total accounts receivable net	265,028	211,846
Trade accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	234,473	190,820
Unbilled accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 34,681	$ 25,657