Bank segment - Loan modifications (Details) - Troubled debt restructurings real estate loans $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	3	3	5	26
Outstanding recorded investment	$ 716	$ 3,075	$ 1,385	$ 13,843
Related allowance	$ 16	$ 304	$ 171	$ 588
Real estate \| Residential 1-4 family
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	2	1	3	16
Outstanding recorded investment	$ 512	$ 442	$ 893	$ 10,363
Related allowance	$ 0	$ 81	$ 135	$ 309
Real estate \| Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	0	0	0
Outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Related allowance	$ 0	$ 0	$ 0	$ 0
Real estate \| Home equity line of credit
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	0	0	0
Outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Related allowance	$ 0	$ 0	$ 0	$ 0
Real estate \| Residential land
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	1	1	1	3
Outstanding recorded investment	$ 204	$ 247	$ 204	$ 802
Related allowance	$ 16	$ 11	$ 16	$ 37
Real estate \| Commercial construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	0	0	0
Outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Related allowance	$ 0	$ 0	$ 0	$ 0
Real estate \| Residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	0	0	0
Outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Related allowance	$ 0	$ 0	$ 0	$ 0
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	1	1	7
Outstanding recorded investment	$ 0	$ 2,386	$ 288	$ 2,678
Related allowance	$ 0	$ 212	$ 20	$ 242
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts \| contract	0	0	0	0
Outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Related allowance	$ 0	$ 0	$ 0	$ 0

Amount of increase (decrease) in allowance for credit loss on financing receivable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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