Supplemental Cash Flow Information - Summary (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest and financing charges, net of capitalized interest	$ 60,403	$ 60,580	$ 49,593
Net cash paid (received) for taxes	(3,063)	50,630	(29,157)
Non-cash additions to property, plant and equipment, including capital leases	$ 8,879	$ 4,748	$ 10,129