Schedule of Net Periodic Benefit Cost (Detail) - Pension Plan and Supplemental Plan - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Net Period Benefit Cost Assumptions [Line Items]
Service cost	$ 1,182	$ 1,371	$ 825
Interest cost	3,814	3,781	3,873
Expected return on plan assets	(2,246)	(2,163)	(2,741)
Administrational expenses	28	36
Payroll tax of net pension costs	56	66
Amortization of prior service cost		36	50
Amortization of net actuarial losses	32	24
Recognized actuarial loss	1,785	2,269	988
Settlement (gain)		(245)
Net periodic pension cost	$ 4,651	$ 5,175	$ 2,995