Bank segment - Principal balance of impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Recorded investment:
With no related allowance recorded	$ 16,436	$ 16,436	$ 23,167
With an allowance recorded	37,610	37,610	26,679
Recorded investment	54,046	54,046	49,846
Unpaid principal balance:
With no related allowance recorded	20,406	20,406	28,890
With an allowance recorded	40,078	40,078	27,119
Unpaid principal balance	60,484	60,484	56,009
Related Allowance	5,867	5,867	4,665
Average recorded investment:
With no related allowance recorded	18,187	20,413	17,592
With an allowance recorded	35,971	30,257	30,882
Average recorded investment	54,158	50,670	48,474
Interest income recognized:
With no related allowance recorded	226	620	442
With an allowance recorded	367	890	1,825
Interest income recognized	593	1,510	2,267
Residential 1-4 family
Recorded investment:
With no related allowance recorded	11,125	11,125	11,654
With an allowance recorded	11,435	11,435	11,327
Recorded investment	22,560	22,560	22,981
Unpaid principal balance:
With no related allowance recorded	12,476	12,476	12,987
With an allowance recorded	11,488	11,488	11,347
Unpaid principal balance	23,964	23,964	24,334
Related Allowance	1,388	1,388	951
Average recorded investment:
With no related allowance recorded	11,159	11,301	9,056
With an allowance recorded	11,451	11,585	8,822
Average recorded investment	22,610	22,886	17,878
Interest income recognized:
With no related allowance recorded	119	274	227
With an allowance recorded	174	430	419
Interest income recognized	293	704	646
Commercial real estate
Recorded investment:
With no related allowance recorded	0	0	571
With an allowance recorded	0	0	4,541
Recorded investment	0	0	5,112
Unpaid principal balance:
With no related allowance recorded	0	0	626
With an allowance recorded	0	0	4,541
Unpaid principal balance	0	0	5,167
Related Allowance	0	0	1,845
Average recorded investment:
With no related allowance recorded	0	362	194
With an allowance recorded	0	1,985	3,415
Average recorded investment	0	2,347	3,609
Interest income recognized:
With no related allowance recorded	74	74	0
With an allowance recorded	0	0	478
Interest income recognized	74	74	478
Home equity line of credit
Recorded investment:
With no related allowance recorded	507	507	363
With an allowance recorded	2,402	2,402	416
Recorded investment	2,909	2,909	779
Unpaid principal balance:
With no related allowance recorded	744	744	606
With an allowance recorded	2,464	2,464	420
Unpaid principal balance	3,208	3,208	1,026
Related Allowance	469	469	46
Average recorded investment:
With no related allowance recorded	498	444	402
With an allowance recorded	2,048	1,295	132
Average recorded investment	2,546	1,739	534
Interest income recognized:
With no related allowance recorded	1	3	5
With an allowance recorded	13	27	6
Interest income recognized	14	30	11
Residential land
Recorded investment:
With no related allowance recorded	1,652	1,652	2,344
With an allowance recorded	4,058	4,058	5,506
Recorded investment	5,710	5,710	7,850
Unpaid principal balance:
With no related allowance recorded	2,421	2,421	3,200
With an allowance recorded	4,136	4,136	5,584
Unpaid principal balance	6,557	6,557	8,784
Related Allowance	919	919	1,057
Average recorded investment:
With no related allowance recorded	2,280	2,647	2,728
With an allowance recorded	3,971	4,435	6,415
Average recorded investment	6,251	7,082	9,143
Interest income recognized:
With no related allowance recorded	29	125	172
With an allowance recorded	74	241	484
Interest income recognized	103	366	656
Commercial loans
Recorded investment:
With no related allowance recorded	3,152	3,152	8,235
With an allowance recorded	19,701	19,701	4,873
Recorded investment	22,853	22,853	13,108
Unpaid principal balance:
With no related allowance recorded	4,765	4,765	11,471
With an allowance recorded	21,976	21,976	5,211
Unpaid principal balance	26,741	26,741	16,682
Related Allowance	3,084	3,084	760
Average recorded investment:
With no related allowance recorded	4,250	5,659	5,204
With an allowance recorded	18,487	10,942	12,089
Average recorded investment	22,737	16,601	17,293
Interest income recognized:
With no related allowance recorded	3	144	38
With an allowance recorded	106	192	438
Interest income recognized	109	336	476
Consumer loans
Recorded investment:
With no related allowance recorded			0
With an allowance recorded	14	14	16
Recorded investment	14	14	16
Unpaid principal balance:
With no related allowance recorded			0
With an allowance recorded	14	14	16
Unpaid principal balance	14	14	16
Related Allowance	7	7	6
Average recorded investment:
With no related allowance recorded			8
With an allowance recorded	14	15	9
Average recorded investment	14	15	17
Interest income recognized:
With an allowance recorded	$ 0	$ 0	$ 0