Investment Securities - Summary of Amortized Cost and Fair Value of Securities (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Abstract]
Amortized cost	$ 1,678,270,000	$ 1,705,574,000
Gross unrealized gains	967,000	458,000
Gross unrealized losses	(208,232,000)	(234,846,000)
Allowance for credit losses for investments	0	0
Fair Value	1,471,005,000	1,471,186,000
U.S. government agency securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	45,176,000	45,167,000
Gross unrealized gains	0	0
Gross unrealized losses	(4,248,000)	(5,105,000)
Allowance for credit losses for investments	0	0
Fair Value	40,928,000	40,062,000
Mortgage-backed securities - residential
Debt Securities, Available-for-sale [Abstract]
Amortized cost	1,197,702,000	1,224,522,000
Gross unrealized gains	0	0
Gross unrealized losses	(172,314,000)	(190,329,000)
Allowance for credit losses for investments	0	0
Fair Value	1,025,388,000	1,034,193,000
Mortgage-backed securities - commercial
Debt Securities, Available-for-sale [Abstract]
Amortized cost	18,979,000	19,209,000
Gross unrealized gains	0	0
Gross unrealized losses	(1,256,000)	(1,565,000)
Allowance for credit losses for investments	0	0
Fair Value	17,723,000	17,644,000
Municipal securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	295,010,000	295,375,000
Gross unrealized gains	967,000	458,000
Gross unrealized losses	(24,983,000)	(31,413,000)
Allowance for credit losses for investments	0	0
Fair Value	270,994,000	264,420,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	113,403,000	113,301,000
Gross unrealized gains	0	0
Gross unrealized losses	(4,580,000)	(5,621,000)
Allowance for credit losses for investments	0	0
Fair Value	108,823,000	107,680,000
Corporate securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	8,000,000	8,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(851,000)	(813,000)
Allowance for credit losses for investments	0	0
Fair Value	$ 7,149,000	$ 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).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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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

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-Name Accounting Standards Codification
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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).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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