Investment Securities - Reconciliation of Available-for-Sale and Held-to-Maturity Securities in Continuous Unrealized Loss Position (Detail) $ in Thousands	Jun. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Fair Value
Less Than 12 Months	$ 344,846	$ 174,022
12 Months or Longer	33,825	23,308
Total	$ 378,671	$ 197,330
Number of Securities | security	136	61
Unrealized Losses
Less Than 12 Months	$ 5,878	$ 977
12 Months or Longer	199	353
Total	6,077	1,330
Fair Value
Less Than 12 Months	20,061	2,561
12 Months or Longer	111	0
Total	20,172	2,561
Unrealized Losses
Less Than 12 Months	301	12
12 Months or Longer	1	0
Total	$ 302	$ 12
Number of Securities | security	16	4
U.S. Treasury and U.S. government agencies
Fair Value
Less Than 12 Months	$ 10,460	$ 4,966
12 Months or Longer	12,083	17,652
Total	$ 22,543	$ 22,618
Number of Securities | security	6	6
Unrealized Losses
Less Than 12 Months	$ 435	$ 29
12 Months or Longer	161	284
Total	596	313
Mortgage-backed securities, residential
Fair Value
Less Than 12 Months	221,699	84,137
12 Months or Longer	4,068	5,656
Total	$ 225,767	$ 89,793
Number of Securities | security	62	30
Unrealized Losses
Less Than 12 Months	$ 3,354	$ 471
12 Months or Longer	10	69
Total	3,364	540
Fair Value
Less Than 12 Months	15,320	2,561
12 Months or Longer	111	0
Total	15,431	2,561
Unrealized Losses
Less Than 12 Months	253	12
12 Months or Longer	1	0
Total	$ 254	$ 12
Number of Securities | security	11	4
Collateralized mortgage obligations, residential
Fair Value
Less Than 12 Months	$ 21,314	$ 23,858
12 Months or Longer	0	0
Total	$ 21,314	$ 23,858
Number of Securities | security	7	7
Unrealized Losses
Less Than 12 Months	$ 312	$ 22
12 Months or Longer	0	0
Total	312	22
Mortgage-backed securities, multifamily
Fair Value
Less Than 12 Months	1,900	1,943
12 Months or Longer	0	0
Total	$ 1,900	$ 1,943
Number of Securities | security	1	1
Unrealized Losses
Less Than 12 Months	$ 38	$ 0
12 Months or Longer	0	0
Total	38	0
Collateralized mortgage obligations, multifamily
Fair Value
Less Than 12 Months	1,543	2,527
12 Months or Longer	0	0
Total	$ 1,543	$ 2,527
Number of Securities | security	1	1
Unrealized Losses
Less Than 12 Months	$ 30	$ 2
12 Months or Longer	0	0
Total	30	2
Asset-backed securities
Fair Value
Less Than 12 Months	7,577	40,690
12 Months or Longer	17,674	0
Total	$ 25,251	$ 40,690
Number of Securities | security	3	6
Unrealized Losses
Less Than 12 Months	$ 27	$ 225
12 Months or Longer	28	0
Total	55	225
Obligations of states and political subdivisions
Fair Value
Less Than 12 Months	77,380	15,901
12 Months or Longer	0	0
Total	$ 77,380	$ 15,901
Number of Securities | security	54	10
Unrealized Losses
Less Than 12 Months	$ 1,673	$ 228
12 Months or Longer	0	0
Total	1,673	$ 228
Fair Value
Less Than 12 Months	4,741
12 Months or Longer	0
Total	4,741
Unrealized Losses
Less Than 12 Months	48
12 Months or Longer	0
Total	$ 48
Number of Securities | security	5
Debt securities
Fair Value
Less Than 12 Months	$ 2,973
12 Months or Longer	0
Total	$ 2,973
Number of Securities | security	2
Unrealized Losses
Less Than 12 Months	$ 9
12 Months or Longer	0
Total	$ 9