Supplemental Cash Flow Information - Components of Change in Other Assets and Liabilities Net (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental Cash Flow Elements [Abstract]
Other current and noncurrent assets	$ (32,572)	$ (29,342)
Accrued salaries, benefits and payroll taxes	5,986	(6,234)
Accrued insurance and other taxes	4,555	10,230
Accrued income taxes	6,220	16,393
Accrued pension, postretirement and postemployment benefits	(131,963)	(5,807)
Other current and noncurrent liabilities	2,769	49,244
Change in other assets and liabilities, net	$ (145,005)	$ 34,484