Bank segment - Credit risk profile - summary (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Credit risk profile based on nonaccrual loans
Nonaccrual loans	$ 27,917	$ 23,591
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	26,224	20,814
Residential 1-4 family
Credit risk profile based on nonaccrual loans
Nonaccrual loans	12,768	12,598
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	10,701	10,982
Commercial real estate
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	981	1,016
Home equity line of credit
Credit risk profile based on nonaccrual loans
Nonaccrual loans	7,191	4,466
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	11,131	6,584
Residential land
Credit risk profile based on nonaccrual loans
Nonaccrual loans	516	841
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	1,542	425
Commercial construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	0	0
Residential construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	0	0
Commercial loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	4,176	3,069
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	1,806	1,741
Consumer loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	3,266	2,617
Accruing loans 90 days or more past due	0	0
Total troubled debt restructuring loans not included above	$ 63	$ 66

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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+ References

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