Bank segment - Credit risk profile - summary (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2015	Dec. 31, 2014
Credit risk profile based on nonaccrual loans
Nonaccrual loans	$ 45,356	$ 36,886
Accruing loans 90 days or more past due	0	0
Financing Receivable, Modifications, Post-Modification Recorded Investment	22,426	24,107
Residential 1-4 family
Credit risk profile based on nonaccrual loans
Nonaccrual loans	19,987	19,253
Financing Receivable, Modifications, Post-Modification Recorded Investment	14,182	13,525
Commercial real estate
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	5,112
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0
Home equity line of credit
Credit risk profile based on nonaccrual loans
Nonaccrual loans	1,982	1,087
Financing Receivable, Modifications, Post-Modification Recorded Investment	2,297	480
Residential land
Credit risk profile based on nonaccrual loans
Nonaccrual loans	975	720
Accruing loans 90 days or more past due	0
Financing Receivable, Modifications, Post-Modification Recorded Investment	4,735	7,130
Commercial construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0
Residential construction
Credit risk profile based on nonaccrual loans
Nonaccrual loans	0	0
Financing Receivable, Modifications, Post-Modification Recorded Investment	0	0
Commercial loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	21,767	10,053
Accruing loans 90 days or more past due		0
Financing Receivable, Modifications, Post-Modification Recorded Investment	1,212	2,972
Consumer loans
Credit risk profile based on nonaccrual loans
Nonaccrual loans	645	661
Accruing loans 90 days or more past due		0
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 0	$ 0

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953676-111524

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- Definition

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

+ References

Reference 1: 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=35738203&loc=d3e5111-111524

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- Definition

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