Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities [Abstract]
Trade accounts payable	$ 189,940	$ 128,106
Accrued wages, salaries and employee benefits	34,174	49,871
Accrued discounts and allowances	11,292	10,291
Accrued taxes other than income taxes payable	6,570	6,946
Accrued utilities	6,993	6,712
Accrued interest	5,582	12,149
Accrued Transportation Current	2,208	1,761
Other	6,389	7,863
Accounts payable and accrued liabilities	$ 263,148	$ 223,699