Investment Securities - Reconciliation of Available-for-Sale and Held-to-Maturity Securities in Continuous Unrealized Loss Position (Detail) $ in Thousands	Dec. 31, 2019 USD ($) Security	Dec. 31, 2018 USD ($) Security
Fair Value
Less than 12 Months	$ 145,431	$ 33,973
12 Months or Longer	152,543	476,622
Total	297,974	510,595
Unrealized Losses
Less than 12 Months	720	278
12 Months or Longer	1,425	11,923
Total	$ 2,145	$ 12,201
Number of Securities | Security	105	220
Fair Value
Less than 12 Months	$ 15,657	$ 13,971
12 Months or Longer	16,692	103,507
Total	32,349	117,478
Unrealized Losses
Less than 12 Months	52	185
12 Months or Longer	134	2,811
Total	$ 186	$ 2,996
Number of Securities | Security	19	72
U.S. Treasury and U.S. government agencies
Fair Value
Less than 12 Months	$ 11,625	$ 20,588
12 Months or Longer	41,617	120,338
Total	53,242	140,926
Unrealized Losses
Less than 12 Months	39	216
12 Months or Longer	397	2,352
Total	$ 436	$ 2,568
Number of Securities | Security	11	27
Fair Value
Less than 12 Months	$ 3,195	$ 0
12 Months or Longer	5,102	32,348
Total	8,297	32,348
Unrealized Losses
Less than 12 Months	6	0
12 Months or Longer	2	677
Total	$ 8	$ 677
Number of Securities | Security	2	6
Mortgage-backed securities, residential
Fair Value
Less than 12 Months	$ 125,782	$ 10,119
12 Months or Longer	99,489	316,851
Total	225,271	326,970
Unrealized Losses
Less than 12 Months	561	58
12 Months or Longer	990	8,785
Total	$ 1,551	$ 8,843
Number of Securities | Security	86	139
Fair Value
Less than 12 Months	$ 12,462	$ 8,325
12 Months or Longer	10,592	53,761
Total	23,054	62,086
Unrealized Losses
Less than 12 Months	46	59
12 Months or Longer	130	1,779
Total	$ 176	$ 1,838
Number of Securities | Security	16	36
Mortgage-backed securities, multifamily
Fair Value
Less than 12 Months	$ 7,651	$ 1,977
12 Months or Longer	4,878	12,911
Total	12,529	14,888
Unrealized Losses
Less than 12 Months	118	2
12 Months or Longer	5	202
Total	$ 123	$ 204
Number of Securities | Security	3	4
Fair Value
Less than 12 Months	$ 0	$ 0
12 Months or Longer	998	1,818
Total	998	1,818
Unrealized Losses
Less than 12 Months	0	0
12 Months or Longer	2	35
Total	$ 2	$ 35
Number of Securities | Security	1	2
Obligations of states and political subdivisions
Fair Value
Less than 12 Months	$ 373	$ 1,289
12 Months or Longer	6,559	26,522
Total	6,932	27,811
Unrealized Losses
Less than 12 Months	2	2
12 Months or Longer	33	584
Total	$ 35	$ 586
Number of Securities | Security	5	50
Fair Value
Less than 12 Months		$ 1,764
12 Months or Longer		15,580
Total		17,344
Unrealized Losses
Less than 12 Months		8
12 Months or Longer		320
Total		$ 328
Number of Securities | Security		27
Debt securities
Fair Value
Less than 12 Months		$ 3,882
12 Months or Longer		0
Total		3,882
Unrealized Losses
Less than 12 Months		118
12 Months or Longer		0
Total		$ 118
Number of Securities | Security		1