Summary of Changes to Restructuring Accrual (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 30,129	$ 90
Restructuring charges	20,930	96,341
Cash payments / adjustments	(40,638)	(65,586)
Non-cash expense	(2,740)	(716)
Ending Balance	7,681	30,129
Employee severance & termination benefits
Restructuring Cost and Reserve [Line Items]
Beginning Balance	27,886	3
Restructuring charges	13,346	92,246
Cash payments / adjustments	(35,955)	(64,363)
Non-cash expense	(898)
Ending Balance	4,379	27,886
Contractual obligations and other
Restructuring Cost and Reserve [Line Items]
Beginning Balance	2,243	87
Restructuring charges	5,742	3,379
Cash payments / adjustments	(4,683)	(1,223)
Ending Balance	3,302	2,243
Write-off of property, plant and equipment
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,842	716
Non-cash expense	$ (1,842)	$ (716)