Bank segment - Loans Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 6,064,848		$ 6,210,578
Less: Deferred fees and discounts	(27,438)		(29,768)
Allowance for credit losses	(64,796)	$ (66,813)	(74,372)	$ (76,366)	$ (69,068)	$ (72,216)
Loans held for investment, net	5,972,614		6,106,438
Real estate loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	5,179,867		5,195,019
Residential 1-4 family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	2,608,281		2,595,162
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,366,214		1,374,038
Home equity line of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	959,607		1,017,207
Residential land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	19,900		18,364
Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	208,867		172,405
Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	16,998		17,843
Commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	645,571		743,303
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 239,410		$ 272,256