Business Segments - Additional Information (Detail) $ in Thousands	6 Months Ended
	Jun. 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	$ 2,300