Schedule of Net Periodic Benefit Cost (Detail) - Pension Plan and Supplemental Plan - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Net Period Benefit Cost Assumptions [Line Items]
Service cost	$ 1,371	$ 825	$ 790
Interest cost	3,781	3,873	3,581
Expected return on plan assets	(2,163)	(2,741)	(2,871)
Administrational expenses	36
Payroll tax of net pension costs	66
Amortization of prior service cost	36	50	50
Amortization of net actuarial losses	24
Recognized actuarial loss	2,269	988	1,103
Settlement (gain)	(245)
Net periodic pension cost	$ 5,175	$ 2,995	$ 2,653