Business Segments - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) Segment
Segment Reporting Information [Line Items]
Number of reportable business segments | Segment		2
Corporate and Other [Member] | Other Expense [Member]
Segment Reporting Information [Line Items]
Contractual settlement		$ 2,425
Pension and other post retirement benefit income	$ 1,300	$ 3,600