Troubled Debt Restructures - Schedule of Status of Types of Debt Restructuring (Detail) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) Loan Contract	Mar. 31, 2019 USD ($) Contract	Mar. 31, 2020 USD ($) Loan	Mar. 31, 2019 USD ($) Loan
Financing Receivable Modifications [Line Items]
Number of Loans | Contract	4	1
Recorded Investments	$ 6,900		$ 6,900
Paid In Full [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			1	7
Recorded Investments	37	$ 1,018	$ 37	$ 1,018
Paying as Restructured [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			7	6
Recorded Investments	3,315	1,992	$ 3,315	$ 1,992
Converted To Nonaccrual
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			1
Recorded Investments	46		$ 46
Foreclosure/ Default [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			0	1
Recorded Investments	0	242	$ 0	$ 242
Extended Maturity [Member] | Paying as Restructured [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			1
Recorded Investments	221		$ 221
Forgiveness of Principal Other [Member] | Paid In Full [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			1	7
Recorded Investments	37	1,018	$ 37	$ 1,018
Forgiveness of Principal Other [Member] | Paying as Restructured [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			6	6
Recorded Investments	3,094	1,992	$ 3,094	$ 1,992
Forgiveness of Principal Other [Member] | Converted To Nonaccrual
Financing Receivable Modifications [Line Items]
Number of Loans | Loan			1
Recorded Investments	$ 46		$ 46
Forgiveness of Principal Other [Member] | Foreclosure/ Default [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan				1
Recorded Investments		$ 242		$ 242
Interest [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	12
Recorded Investments	$ 11,697		11,697
Interest [Member] | Real Estate - Commercial [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	6
Recorded Investments	$ 11,288		11,288
Interest [Member] | Other Real Estate Construction [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 350		350
Interest [Member] | Commercial Loan [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 35		35
Interest [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	4
Recorded Investments	$ 24		24
Payment Deferral [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	47
Recorded Investments	$ 14,670		14,670
Payment Deferral [Member] | Real Estate - Commercial [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	18
Recorded Investments	$ 11,381		11,381
Payment Deferral [Member] | Real Estate - Residential [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	8
Recorded Investments	$ 1,308		1,308
Payment Deferral [Member] | Home Equity [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 20		20
Payment Deferral [Member] | Commercial Loan [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	7
Recorded Investments	$ 1,327		1,327
Payment Deferral [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	13
Recorded Investments	$ 634		634
Payment Deferral [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	2
Recorded Investments	$ 197		197
Payment Deferral [Member] | Real Estate - Commercial [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 177		177
Payment Deferral [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 20		20
Total COVID-19 modifications [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	61
Recorded Investments	$ 26,564		26,564
Total COVID-19 modifications [Member] | Real Estate - Commercial [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	25
Recorded Investments	$ 22,846		22,846
Total COVID-19 modifications [Member] | Other Real Estate Construction [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 350		350
Total COVID-19 modifications [Member] | Real Estate - Residential [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	8
Recorded Investments	$ 1,308		1,308
Total COVID-19 modifications [Member] | Home Equity [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	1
Recorded Investments	$ 20		20
Total COVID-19 modifications [Member] | Commercial Loan [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	8
Recorded Investments	$ 1,362		1,362
Total COVID-19 modifications [Member] | Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Loans | Loan	18
Recorded Investments	$ 678		$ 678