Fair value measurements - Assets and liabilities measured on a recurring basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair value measurements on a recurring basis
Available-for-sale investment securities	$ 1,419,755	$ 1,429,667
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1)
Derivative assets
Derivative assets	9	18
Derivative liabilities
Derivative liabilities	4	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Bank \| Interest rate lock commitments
Derivative assets
Derivative assets	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Bank \| Forward commitments
Derivative assets
Derivative assets	9	18
Derivative liabilities
Derivative liabilities	4	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Other \| Interest rate swap
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| U.S. Treasury and federal agency obligations \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Corporate bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Quoted prices in active markets for identical assets (Level 1) \| Mortgage revenue bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2)
Derivative assets
Derivative assets	1,133	1,330
Derivative liabilities
Derivative liabilities	0	472
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	1,404,989	1,414,765
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Bank \| Interest rate lock commitments
Derivative assets
Derivative assets	26	9
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Bank \| Forward commitments
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Other \| Interest rate swap
Derivative assets
Derivative assets	1,107	1,321
Derivative liabilities
Derivative liabilities	0	472
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	1,283,935	1,292,968
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| U.S. Treasury and federal agency obligations \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	79,744	81,063
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Corporate bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	41,310	40,734
Fair value measurements on a recurring basis \| Significant other observable inputs (Level 2) \| Mortgage revenue bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3)
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	14,766	14,902
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Bank \| Interest rate lock commitments
Derivative assets
Derivative assets	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Bank \| Forward commitments
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Other \| Interest rate swap
Derivative assets
Derivative assets	0	0
Derivative liabilities
Derivative liabilities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Mortgage-backed securities — issued or guaranteed by U.S. Government agencies or sponsored agencies \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| U.S. Treasury and federal agency obligations \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Corporate bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	0	0
Fair value measurements on a recurring basis \| Significant unobservable inputs (Level 3) \| Mortgage revenue bonds \| Bank
Fair value measurements on a recurring basis
Available-for-sale investment securities	$ 14,766	$ 14,902

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).

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-Publisher FASB
-Name Accounting Standards Codification
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