Investment Securities - Reconciliation of Available-for-Sale and Held-to-Maturity Securities in Continuous Unrealized Loss Position (Detail) $ in Thousands	Mar. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($) Security
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	$ 194,669	$ 145,431
Available for Sale, Less Than 12 Months, Unrealized Losses	3,827	720
Available for Sale, 12 Months or Longer, Fair Value	31,792	152,543
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 679	$ 1,425
Available for Sale, Number of Securities (in shares) \| Security	54	105
Available for Sale, Total, Fair Value	$ 226,461	$ 297,974
Available for Sale, Total, Unrealized Losses	4,506	2,145
Held to Maturity, Less Than 12 Months, Fair Value		15,657
Held to Maturity, Less Than 12 Months, Unrealized Losses		52
Held to Maturity, 12 Months or Longer, Fair Value		16,692
Held to Maturity, 12 Months or Longer, Unrealized Losses		$ 134
Held to Maturity, Number of Securities (in shares) \| Security		19
Held to Maturity, Total, Fair Value		$ 32,349
Held to Maturity, Total, Unrealized Losses		186
U.S. Treasury and U.S. government agencies
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	74,745	11,625
Available for Sale, Less Than 12 Months, Unrealized Losses	28	39
Available for Sale, 12 Months or Longer, Fair Value	19,355	41,617
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 291	$ 397
Available for Sale, Number of Securities (in shares) \| Security	11	11
Available for Sale, Total, Fair Value	$ 94,100	$ 53,242
Available for Sale, Total, Unrealized Losses	319	436
Held to Maturity, Less Than 12 Months, Fair Value		3,195
Held to Maturity, Less Than 12 Months, Unrealized Losses		6
Held to Maturity, 12 Months or Longer, Fair Value		5,102
Held to Maturity, 12 Months or Longer, Unrealized Losses		$ 2
Held to Maturity, Number of Securities (in shares) \| Security		2
Held to Maturity, Total, Fair Value		$ 8,297
Held to Maturity, Total, Unrealized Losses		8
Mortgage-backed securities, residential
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	51,693	125,782
Available for Sale, Less Than 12 Months, Unrealized Losses	919	561
Available for Sale, 12 Months or Longer, Fair Value	8,180	99,489
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 386	$ 990
Available for Sale, Number of Securities (in shares) \| Security	24	86
Available for Sale, Total, Fair Value	$ 59,873	$ 225,271
Available for Sale, Total, Unrealized Losses	1,305	1,551
Held to Maturity, Less Than 12 Months, Fair Value		12,462
Held to Maturity, Less Than 12 Months, Unrealized Losses		46
Held to Maturity, 12 Months or Longer, Fair Value		10,592
Held to Maturity, 12 Months or Longer, Unrealized Losses		$ 130
Held to Maturity, Number of Securities (in shares) \| Security		16
Held to Maturity, Total, Fair Value		$ 23,054
Held to Maturity, Total, Unrealized Losses		176
Mortgage-backed securities, multifamily
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	2,801	7,651
Available for Sale, Less Than 12 Months, Unrealized Losses	16	118
Available for Sale, 12 Months or Longer, Fair Value	4,257	4,878
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 2	$ 5
Available for Sale, Number of Securities (in shares) \| Security	2	3
Available for Sale, Total, Fair Value	$ 7,058	$ 12,529
Available for Sale, Total, Unrealized Losses	18	123
Held to Maturity, Less Than 12 Months, Fair Value		0
Held to Maturity, Less Than 12 Months, Unrealized Losses		0
Held to Maturity, 12 Months or Longer, Fair Value		998
Held to Maturity, 12 Months or Longer, Unrealized Losses		$ 2
Held to Maturity, Number of Securities (in shares) \| Security		1
Held to Maturity, Total, Fair Value		$ 998
Held to Maturity, Total, Unrealized Losses		2
Asset-backed securities
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	41,112
Available for Sale, Less Than 12 Months, Unrealized Losses	1,951
Available for Sale, 12 Months or Longer, Fair Value	0
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 0
Available for Sale, Number of Securities (in shares) \| Security	6
Available for Sale, Total, Fair Value	$ 41,112
Available for Sale, Total, Unrealized Losses	1,951
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available for Sale, Less Than 12 Months, Fair Value	24,318	373
Available for Sale, Less Than 12 Months, Unrealized Losses	913	2
Available for Sale, 12 Months or Longer, Fair Value	0	6,559
Available for Sale, 12 Months or Longer, Unrealized Losses	$ 0	$ 33
Available for Sale, Number of Securities (in shares) \| Security	11	5
Available for Sale, Total, Fair Value	$ 24,318	$ 6,932
Available for Sale, Total, Unrealized Losses	$ 913	$ 35

Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss

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Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value

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Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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