Retirement Plans - Schedule of Net Pension (Benefit) Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Curtailment benefit			$ 0	$ (8,020)
Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period			0	2,042
Interest cost on projected benefit obligation	$ 616	$ 642	1,850	2,024
Expected return on assets	(902)	(951)	(2,706)	(2,275)
Amortization of net prior year service benefit			0	(28)
Curtailment benefit			0	(8,051)
Net pension benefit	(286)	(309)	(856)	(6,288)
Restoration Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period			0	27
Interest cost on projected benefit obligation	17	18	52	54
Amortization of net prior year service benefit	0	2	0	7
Amortization of net actuarial loss	3	6	10	26
Curtailment benefit			0	31
Net pension benefit	$ 20	$ 26	$ 62	$ 145