Bank segment - Loan modifications (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2016 USD ($) contract	Sep. 30, 2015 USD ($) contract	Sep. 30, 2016 USD ($) contract	Sep. 30, 2015 USD ($) contract	Dec. 31, 2015 USD ($)
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			$ 25,740		$ 22,246
Residential 1-4 family
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			13,308		13,962
Commercial real estate
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			0		0
Home equity line of credit
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			4,501		2,467
Residential land
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			3,258		4,713
Commercial construction
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			0		0
Residential construction
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			0		0
Commercial loans
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			4,673		1,104
Consumer loans
Financing Receivable, Modifications [Line Items]
Post-modification outstanding recorded investment			$ 0		$ 0
Troubled debt restructurings real estate loans
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	20	15	56	48
Pre-modification outstanding recorded investment	$ 4,981	$ 3,011	$ 25,183	$ 5,578
Post-modification outstanding recorded investment	4,981	3,017	25,296	5,602
Net increases in ALL	$ 336	$ 157	$ 1,520	$ 442
Troubled debt restructurings real estate loans \| Residential 1-4 family
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	2	3	11	10
Pre-modification outstanding recorded investment	$ 251	$ 860	$ 2,239	$ 2,055
Post-modification outstanding recorded investment	251	866	2,351	2,079
Net increases in ALL	$ 46	$ 1	$ 305	$ 48
Troubled debt restructurings real estate loans \| Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	0	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0	0
Net increases in ALL	$ 0	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Home equity line of credit
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	12	10	30	32
Pre-modification outstanding recorded investment	$ 1,268	$ 943	$ 2,705	$ 2,062
Post-modification outstanding recorded investment	1,268	943	2,705	2,062
Net increases in ALL	$ 237	$ 140	$ 492	$ 300
Troubled debt restructurings real estate loans \| Residential land
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	0	0	1	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 120	$ 0
Post-modification outstanding recorded investment	0	0	121	0
Net increases in ALL	$ 0	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Commercial construction
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	0	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0	0
Net increases in ALL	$ 0	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Residential construction
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	0	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0	0
Net increases in ALL	$ 0	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Commercial loans
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	6	2	14	6
Pre-modification outstanding recorded investment	$ 3,462	$ 1,208	$ 20,119	$ 1,461
Post-modification outstanding recorded investment	3,462	1,208	20,119	1,461
Net increases in ALL	$ 53	$ 16	$ 723	$ 94
Troubled debt restructurings real estate loans \| Consumer loans
Financing Receivable, Modifications [Line Items]
Number of contracts \| contract	0	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0	0
Net increases in ALL	$ 0	$ 0	$ 0	$ 0

Amount of increase (decrease) of allowance reserve for credit loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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+ References

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=66008989&loc=SL6953676-111524

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