Bank segment - Loans receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 5,193,260	$ 5,221,204
Less: Deferred fees and discounts	(8,527)	(10,090)
Allowance for credit losses	(67,211)	(71,130)	$ (91,793)	$ (101,201)
Total loans, net	5,117,522	5,139,984
Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	4,368,723	4,313,934
Real estate | Residential 1-4 family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,279,671	2,299,212
Allowance for credit losses	(7,874)	(6,545)	(5,261)	(4,600)
Real estate | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,115,632	1,056,982
Allowance for credit losses	(20,176)	(24,696)	(34,345)	(35,607)
Real estate | Home equity line of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	845,271	835,663
Allowance for credit losses	(5,650)	(5,657)	(5,901)	(6,813)
Real estate | Residential land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	22,309	19,859
Allowance for credit losses	(697)	(646)	(573)	(609)
Real estate | Commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	90,332	91,080
Allowance for credit losses	(2,340)	(2,186)	(1,453)	(4,149)
Real estate | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	15,508	11,138
Allowance for credit losses	(31)	(18)	(16)	(11)
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	708,447	793,304
Allowance for credit losses	(14,314)	(15,798)	(24,504)	(25,462)
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	116,090	113,966
Allowance for credit losses	$ (16,129)	$ (15,584)	$ (19,740)	$ (23,950)