Bank segment - Credit risk profile - payment activity (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Credit risk profile based on payment activity for loans
Total past due	$ 24,549	$ 26,099
Current	4,623,107	4,595,969
Total financing receivables	4,647,656	4,622,068
Recorded Investment greater than 90 days and accruing	0	0
Residential 1-4 family
Credit risk profile based on payment activity for loans
Total past due	18,378	19,759
Current	2,036,642	2,049,906
Total financing receivables	2,055,020	2,069,665
Commercial real estate
Credit risk profile based on payment activity for loans
Current	703,661	690,561
Total financing receivables	703,661	690,561
Home equity line of credit
Credit risk profile based on payment activity for loans
Total past due	2,066	2,079
Current	844,401	844,215
Total financing receivables	846,467	846,294
Residential land
Credit risk profile based on payment activity for loans
Total past due	148	415
Current	18,792	17,814
Total financing receivables	18,940	18,229
Commercial construction
Credit risk profile based on payment activity for loans
Current	130,487	100,796
Total financing receivables	130,487	100,796
Residential construction
Credit risk profile based on payment activity for loans
Current	16,241	14,089
Total financing receivables	16,241	14,089
Commercial loans
Credit risk profile based on payment activity for loans
Total past due	1,683	1,226
Current	738,913	757,433
Total financing receivables	740,596	758,659
Consumer loans
Credit risk profile based on payment activity for loans
Total past due	2,274	2,620
Current	133,970	121,155
Total financing receivables	136,244	123,775
Financing Receivables, 30 to 59 Days Past Due [Member]
Credit risk profile based on payment activity for loans
Total past due	8,395	7,371
Financing Receivables, 30 to 59 Days Past Due [Member] \| Residential 1-4 family
Credit risk profile based on payment activity for loans
Total past due	5,537	4,967
Financing Receivables, 30 to 59 Days Past Due [Member] \| Home equity line of credit
Credit risk profile based on payment activity for loans
Total past due	1,218	896
Financing Receivables, 30 to 59 Days Past Due [Member] \| Residential land
Credit risk profile based on payment activity for loans
Total past due	0
Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial loans
Credit risk profile based on payment activity for loans
Total past due	391	125
Financing Receivables, 30 to 59 Days Past Due [Member] \| Consumer loans
Credit risk profile based on payment activity for loans
Total past due	1,249	1,383
Financing Receivables, 60 to 89 Days Past Due [Member]
Credit risk profile based on payment activity for loans
Total past due	4,286	4,811
Financing Receivables, 60 to 89 Days Past Due [Member] \| Residential 1-4 family
Credit risk profile based on payment activity for loans
Total past due	2,215	3,289
Financing Receivables, 60 to 89 Days Past Due [Member] \| Home equity line of credit
Credit risk profile based on payment activity for loans
Total past due	508	706
Financing Receivables, 60 to 89 Days Past Due [Member] \| Residential land
Credit risk profile based on payment activity for loans
Total past due	0
Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial loans
Credit risk profile based on payment activity for loans
Total past due	984	223
Financing Receivables, 60 to 89 Days Past Due [Member] \| Consumer loans
Credit risk profile based on payment activity for loans
Total past due	579	593
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Credit risk profile based on payment activity for loans
Total past due	11,868	13,917
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Residential 1-4 family
Credit risk profile based on payment activity for loans
Total past due	10,626	11,503
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Home equity line of credit
Credit risk profile based on payment activity for loans
Total past due	340	477
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Residential land
Credit risk profile based on payment activity for loans
Total past due	148	415
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial loans
Credit risk profile based on payment activity for loans
Total past due	308	878
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Consumer loans
Credit risk profile based on payment activity for loans
Total past due	$ 446	$ 644

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

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- Definition

Financing receivables that are current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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