Schedule of Net Periodic Benefit Costs (Detail) - Pension Benefits - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Period Benefit Cost Assumptions [Line Items]
Service cost	$ 316	$ 47	$ 328	$ 118
Interest cost	1,006	872	2,853	2,656
Expected return on plan assets	(711)	(481)	(1,787)	(1,446)
Administrative expenses	83	3	90	6
Settlement loss recognized	(46)		46	335
Net periodic pension cost	$ 648	$ 441	$ 1,530	$ 1,669