Litigation - Summary of Activity in Asbestos Insurance Recoveries (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Insurance receivable - asbestos, beginning of the year	$ 115,945
Insurance receivable - asbestos, end of the year	100,342	$ 115,945
Asbestos Claims [Member]
Loss Contingencies [Line Items]
Insurance receivable - asbestos, beginning of the year	115,945	125,423
Settlement and defense costs paid by insurance carriers	(15,603)	(23,138)
Changes in estimated coverage	0	13,660
Insurance receivable - asbestos, end of the year	$ 100,342	$ 115,945