Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Abstract]
Trade accounts payable	$ 180,394	$ 169,293
Accrued wages, salaries and employee benefits	32,538	41,979
Accrued discounts and allowances	7,142	7,283
Accrued taxes other than income taxes payable	7,372	6,907
Accrued utilities	5,994	6,759
Accrued interest	5,549	12,723
Other	10,348	11,677
Accounts payable and accrued liabilities	$ 249,337	$ 256,621