Investment Securities - Summary of Amortized Cost and Fair Value of Securities (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Abstract]
Total debt securities	$ 1,645,373,000	$ 1,705,574,000
Gross unrealized gains	387,000	458,000
Gross unrealized losses	(226,400,000)	(234,846,000)
Allowance for credit losses for investments	0	0
Fair Value	1,419,360,000	1,471,186,000
U.S. government agency securities
Debt Securities, Available-for-sale [Abstract]
Total debt securities	45,185,000	45,167,000
Gross unrealized gains	0	0
Gross unrealized losses	(4,656,000)	(5,105,000)
Allowance for credit losses for investments	0	0
Fair Value	40,529,000	40,062,000
Mortgage-backed securities - residential
Debt Securities, Available-for-sale [Abstract]
Total debt securities	1,165,901,000	1,224,522,000
Gross unrealized gains	0	0
Gross unrealized losses	(186,501,000)	(190,329,000)
Allowance for credit losses for investments	0	0
Fair Value	979,400,000	1,034,193,000
Mortgage-backed securities - commercial
Debt Securities, Available-for-sale [Abstract]
Total debt securities	18,747,000	19,209,000
Gross unrealized gains	0	0
Gross unrealized losses	(1,493,000)	(1,565,000)
Allowance for credit losses for investments	0	0
Fair Value	17,254,000	17,644,000
Municipal securities
Debt Securities, Available-for-sale [Abstract]
Total debt securities	294,032,000	295,375,000
Gross unrealized gains	387,000	458,000
Gross unrealized losses	(27,322,000)	(31,413,000)
Allowance for credit losses for investments	0	0
Fair Value	267,097,000	264,420,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Abstract]
Total debt securities	113,508,000	113,301,000
Gross unrealized gains	0	0
Gross unrealized losses	(5,287,000)	(5,621,000)
Allowance for credit losses for investments	0	0
Fair Value	108,221,000	107,680,000
Corporate securities
Debt Securities, Available-for-sale [Abstract]
Total debt securities	8,000,000	8,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(1,141,000)	(813,000)
Allowance for credit losses for investments	0	0
Fair Value	$ 6,859,000	$ 7,187,000

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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