Schedule of Reconciliation of Obligations and Fair Values of Plan Assets (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Benefit Obligation at April 1,		$ 40,589	$ 42,281
Service Cost - Benefits Earned During the Period		710	1,001	$ 1,039
Interest Cost on Projected Benefit Obligation		1,466	1,584	1,525
Amendments			199
Actuarial (Gain) Loss		(4,505)	(3,531)
Settlement	$ (3,900)	(3,857)
Benefits Paid		(1,033)	(945)
Benefit Obligation at March 31,	33,370	33,370	40,589	42,281
Fair Value of Plan Assets at April 1,		26,410	21,424
Actual Return on Plan Assets		2,805	2,522
Employer Contributions		9,087	3,409
Settlement		(3,857)
Benefits Paid		(1,033)	(945)
Fair Value of Plans at March 31,	33,412	33,412	26,410	$ 21,424
Funded (Unfunded) Status at March 31,	42	42	(14,179)
Prepaid and Other Assets	538	538
Accrued Benefit Liability	(496)	(496)	(14,179)
Accumulated Other Comprehensive Losses:	5,278	5,278	11,936
Accumulated Other Comprehensive Losses - Net Actuarial Loss	5,198	5,198	11,587
Accumulated Other Comprehensive Losses - Prior Service Cost	80	80	349
Accumulated Other Comprehensive Losses	5,278	5,278	11,936
Reclassification to Retained Earnings	978	978
Tax impact	(2,244)	(2,244)	(4,540)
Accumulated Other Comprehensive Losses, net of tax	$ 4,012	$ 4,012	$ 7,396