Securities - Summary of Unrealized Loss Information for Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 37,699	$ 186,692
Less than 12 months Unrealized Losses	185	1,125
12 months or more Fair Value	6,217	100,790
12 months or more Unrealized Losses	27	1,274
Total Fair Value	43,916	287,482
Total Unrealized Losses	212	2,399
Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		76,682
Less than 12 months Unrealized Losses		217
12 months or more Fair Value		20,429
12 months or more Unrealized Losses		72
Total Fair Value		97,111
Total Unrealized Losses		289
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	25,319	101,730
Less than 12 months Unrealized Losses	93	871
12 months or more Fair Value	5,566	76,630
12 months or more Unrealized Losses	25	1,179
Total Fair Value	30,885	178,360
Total Unrealized Losses	118	2,050
State, County and Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	12,380	8,280
Less than 12 months Unrealized Losses	92	37
12 months or more Fair Value	651	3,731
12 months or more Unrealized Losses	2	23
Total Fair Value	13,031	12,011
Total Unrealized Losses	$ 94	$ 60