Securities Available for Sale - Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Detail) - Debt Securities [Member] $ in Thousands	Mar. 31, 2021 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	$ (317)
Less Than Twelve Months, Fair Value	17,972
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(90)
Less Than Twelve Months, Fair Value	3,823
US Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(2)
Less Than Twelve Months, Fair Value	1,992
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(5)
Less Than Twelve Months, Fair Value	1,801
Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than Twelve Months, Gross Unrealized Losses	(220)
Less Than Twelve Months, Fair Value	$ 10,356