Bank segment - Credit risk profile - nonaccrual loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Credit risk profile based on nonaccrual loans
Nonaccrual loans	$ 46,766	$ 29,736
Total troubled debt restructuring loans not included above	25,856	26,413
Residential 1-4 family
Credit risk profile based on nonaccrual loans
Nonaccrual loans	10,747	11,395
Total troubled debt restructuring loans not included above	9,254	9,869
Commercial real estate
Credit risk profile based on nonaccrual loans
Nonaccrual loans	16,390	195
Total troubled debt restructuring loans not included above	1,035	853
Nonaccrual loans with no related allowance	2,300
Home equity line of credit
Credit risk profile based on nonaccrual loans
Nonaccrual loans	6,596	6,638
Total troubled debt restructuring loans not included above	9,628	10,376
Nonaccrual loans with no related allowance	1,800
Residential land
Credit risk profile based on nonaccrual loans
Nonaccrual loans	413	448
Total troubled debt restructuring loans not included above	2,622	2,644
Nonaccrual loans with no related allowance	4,100
Commercial construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	2,289	0
Total troubled debt restructuring loans not included above	0	0
Residential construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Total troubled debt restructuring loans not included above	0	0
Commercial loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	5,366	5,947
Total troubled debt restructuring loans not included above	3,261	2,614
Nonaccrual loans with no related allowance	5,100
Consumer loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	4,965	5,113
Total troubled debt restructuring loans not included above	$ 56	$ 57

Amount, after troubled debt restructuring, of modified financing receivable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919258-210447

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