Investment Securities - Summary of Amortized Cost and Fair Value of Securities (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Abstract]
Amortized cost	$ 1,784,458,000	$ 1,673,798,000
Gross unrealized gains	4,232,000	23,120,000
Gross unrealized losses	(105,165,000)	(18,393,000)
Allowance for credit losses for investments	0	0
Fair Value	1,683,525,000	1,678,525,000
U.S. government agency securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	41,015,000	34,023,000
Gross unrealized gains	0	18,000
Gross unrealized losses	(2,133,000)	(171,000)
Allowance for credit losses for investments	0	0
Fair Value	38,882,000	33,870,000
Mortgage-backed securities - residential
Debt Securities, Available-for-sale [Abstract]
Amortized cost	1,320,205,000	1,281,285,000
Gross unrealized gains	616,000	6,072,000
Gross unrealized losses	(88,565,000)	(17,985,000)
Allowance for credit losses for investments	0	0
Fair Value	1,232,256,000	1,269,372,000
Mortgage-backed securities - commercial
Debt Securities, Available-for-sale [Abstract]
Amortized cost	14,738,000	15,024,000
Gross unrealized gains	14,000	272,000
Gross unrealized losses	(445,000)	(46,000)
Allowance for credit losses for investments	0	0
Fair Value	14,307,000	15,250,000
Municipal securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	318,587,000	322,052,000
Gross unrealized gains	3,594,000	16,718,000
Gross unrealized losses	(12,043,000)	(160,000)
Allowance for credit losses for investments	0	0
Fair Value	310,138,000	338,610,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	81,913,000	14,914,000
Gross unrealized gains	4,000	0
Gross unrealized losses	(1,744,000)	(6,000)
Allowance for credit losses for investments	0	0
Fair Value	80,173,000	14,908,000
Corporate securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost	8,000,000	6,500,000
Gross unrealized gains	4,000	40,000
Gross unrealized losses	(235,000)	(25,000)
Allowance for credit losses for investments	0	0
Fair Value	$ 7,769,000	$ 6,515,000

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).

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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
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