Loans - Schedule of Loan Assigned Risk Rating within 12 Months of Balance Sheet Date (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	$ 949,679	$ 923,543
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	477,835	475,364
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	471,844	448,179
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	899,069	874,319
Pass [Member] | Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	448,196	447,449
Pass [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	450,873	426,870
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	9,845	6,484
Special Mention [Member] | Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	8,113	4,749
Special Mention [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	1,732	1,735
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	40,090	42,091
Substandard [Member] | Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	21,274	22,943
Substandard [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	18,816	19,148
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	675	649
Doubtful [Member] | Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	252	223
Doubtful [Member] | Commercial Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivable recorded investment	$ 423	$ 426