Bank segment - Credit risk profile - payment activity (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Credit risk profile based on payment activity for loans
30-59 days past due	$ 9,112	$ 8,993
60-89 days past due	4,033	2,711
Greater than 90 days	13,658	13,798
Total past due	26,803	25,502
Current	4,426,728	4,415,487
Total financing receivables	4,453,531us-gaap_NotesReceivableNet	4,440,989us-gaap_NotesReceivableNet	4,196,369us-gaap_NotesReceivableNet
Recorded Investment greater than 90 days and accruing	0	0
Residential 1-4 family
Credit risk profile based on payment activity for loans
30-59 days past due	6,074	6,124
60-89 days past due	2,718	1,732
Greater than 90 days	12,231	12,632
Total past due	21,023	20,488
Current	2,018,076	2,023,717
Total financing receivables	2,039,099	2,044,205	1,985,812
Commercial real estate
Credit risk profile based on payment activity for loans
30-59 days past due	0	0
Greater than 90 days	0	0
Total past due	0	0
Current	561,189	531,917
Total financing receivables	561,189	531,917	452,303
Home equity line of credit
Credit risk profile based on payment activity for loans
30-59 days past due	1,041	1,341
60-89 days past due	807	501
Greater than 90 days	629	194
Total past due	2,477	2,036
Current	811,788	816,779
Total financing receivables	814,265	818,815	764,483
Residential land
Credit risk profile based on payment activity for loans
30-59 days past due	422	0
60-89 days past due	0	0
Greater than 90 days	0	0
Total past due	422	0
Current	17,733	16,240
Total financing receivables	18,155	16,240	15,906
Recorded Investment greater than 90 days and accruing
Commercial construction
Credit risk profile based on payment activity for loans
Current	77,164	96,438
Total financing receivables	77,164	96,438	66,578
Residential construction
Credit risk profile based on payment activity for loans
Current	20,804	18,961
Total financing receivables	20,804	18,961	16,474
Commercial loans
Credit risk profile based on payment activity for loans
30-59 days past due	680	699
60-89 days past due	238	145
Greater than 90 days	532	569
Total past due	1,450	1,413
Current	802,095	790,344
Total financing receivables	803,545	791,757	786,611
Recorded Investment greater than 90 days and accruing		0
Consumer loans
Credit risk profile based on payment activity for loans
30-59 days past due	895	829
60-89 days past due	270	333
Greater than 90 days	266	403
Total past due	1,431	1,565
Current	117,879	121,091
Total financing receivables	119,310	122,656	108,202
Recorded Investment greater than 90 days and accruing		$ 0

Financing receivables that are less than 60 days past due but more than 29 days past due.

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=35738203&loc=SL6953401-111524

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- Definition

Financing receivables that are less than 90 days past due but more than 59 days past due.

+ References

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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

Financing receivables that are current.

+ References

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- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

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- Definition

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

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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Article 5

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