Securities - Gross Unrealized Losses, Aggregated by Investment Category and Length of Time (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	$ (11,483)	$ (4,842)
Fair Value, Less Than Twelve Months	235,645	256,800
Gross Unrealized Losses, Twelve Months and Over	(13,774)	(2,221)
Fair Value, Twelve Months and Over	154,116	63,659
Gross Unrealized Losses, Total	(25,257)	(7,063)
Fair Value, Total	389,761	320,459
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(3,481)	(1,598)
Fair Value, Less Than Twelve Months	73,310	89,177
Gross Unrealized Losses, Twelve Months and Over	(2,368)
Fair Value, Twelve Months and Over	26,235
Gross Unrealized Losses, Total	(5,849)	(1,598)
Fair Value, Total	99,545	89,177
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(2,546)	(1,898)
Fair Value, Less Than Twelve Months	48,126	86,739
Gross Unrealized Losses, Twelve Months and Over	(7,272)	(1,584)
Fair Value, Twelve Months and Over	86,553	41,738
Gross Unrealized Losses, Total	(9,818)	(3,482)
Fair Value, Total	134,679	128,477
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(3,271)	(1,050)
Fair Value, Less Than Twelve Months	65,991	63,157
Gross Unrealized Losses, Twelve Months and Over	(3,228)	(412)
Fair Value, Twelve Months and Over	34,388	16,434
Gross Unrealized Losses, Total	(6,499)	(1,462)
Fair Value, Total	100,379	79,591
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(2,185)	(296)
Fair Value, Less Than Twelve Months	48,218	17,727
Gross Unrealized Losses, Twelve Months and Over	(906)	(225)
Fair Value, Twelve Months and Over	6,940	5,487
Gross Unrealized Losses, Total	(3,091)	(521)
Fair Value, Total	$ 55,158	$ 23,214