Bank segment - Principal balance of impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Recorded investment:
With no related allowance recorded	$ 21,608	$ 23,167
With an allowance recorded	27,375	26,679
Recorded investment	48,983	49,846
Unpaid principal balance:
With no related allowance recorded	25,823	28,890
With an allowance recorded	29,581	27,119
Unpaid principal balance	55,404	56,009
Related Allowance	5,548	4,665
Average recorded investment:
With no related allowance recorded	22,439	17,592
With an allowance recorded	26,804	30,882
Average recorded investment	49,243	48,474
Interest income recognized:
With no related allowance recorded	144	442
With an allowance recorded	265	1,825
Interest income recognized	409	2,267
Residential 1-4 family
Recorded investment:
With no related allowance recorded	11,168	11,654
With an allowance recorded	11,921	11,327
Recorded investment	23,089	22,981
Unpaid principal balance:
With no related allowance recorded	12,460	12,987
With an allowance recorded	11,974	11,347
Unpaid principal balance	24,434	24,334
Related Allowance	1,429	951
Average recorded investment:
With no related allowance recorded	11,552	9,056
With an allowance recorded	11,510	8,822
Average recorded investment	23,062	17,878
Interest income recognized:
With no related allowance recorded	89	227
With an allowance recorded	126	419
Interest income recognized	215	646
Commercial real estate
Recorded investment:
With no related allowance recorded	547	571
With an allowance recorded	4,451	4,541
Recorded investment	4,998	5,112
Unpaid principal balance:
With no related allowance recorded	609	626
With an allowance recorded	4,511	4,541
Unpaid principal balance	5,120	5,167
Related Allowance	1,785	1,845
Average recorded investment:
With no related allowance recorded	555	194
With an allowance recorded	4,482	3,415
Average recorded investment	5,037	3,609
Interest income recognized:
With no related allowance recorded		0
With an allowance recorded	0	478
Interest income recognized	0	478
Home equity line of credit
Recorded investment:
With no related allowance recorded	339	363
With an allowance recorded	844	416
Recorded investment	1,183	779
Unpaid principal balance:
With no related allowance recorded	544	606
With an allowance recorded	900	420
Unpaid principal balance	1,444	1,026
Related Allowance	144	46
Average recorded investment:
With no related allowance recorded	400	402
With an allowance recorded	626	132
Average recorded investment	1,026	534
Interest income recognized:
With no related allowance recorded	1	5
With an allowance recorded	6	6
Interest income recognized	7	11
Residential land
Recorded investment:
With no related allowance recorded	3,265	2,344
With an allowance recorded	4,554	5,506
Recorded investment	7,819	7,850
Unpaid principal balance:
With no related allowance recorded	4,121	3,200
With an allowance recorded	4,632	5,584
Unpaid principal balance	8,753	8,784
Related Allowance	1,085	1,057
Average recorded investment:
With no related allowance recorded	2,637	2,728
With an allowance recorded	5,189	6,415
Average recorded investment	7,826	9,143
Interest income recognized:
With no related allowance recorded	52	172
With an allowance recorded	83	484
Interest income recognized	135	656
Commercial loans
Recorded investment:
With no related allowance recorded	6,289	8,235
With an allowance recorded	5,590	4,873
Recorded investment	11,879	13,108
Unpaid principal balance:
With no related allowance recorded	8,089	11,471
With an allowance recorded	7,549	5,211
Unpaid principal balance	15,638	16,682
Related Allowance	1,096	760
Average recorded investment:
With no related allowance recorded	7,295	5,204
With an allowance recorded	4,982	12,089
Average recorded investment	12,277	17,293
Interest income recognized:
With no related allowance recorded	2	38
With an allowance recorded	50	438
Interest income recognized	52	476
Consumer loans
Recorded investment:
With no related allowance recorded	0	0
With an allowance recorded	15	16
Recorded investment	15	16
Unpaid principal balance:
With no related allowance recorded	0	0
With an allowance recorded	15	16
Unpaid principal balance	15	16
Related Allowance	9	6
Average recorded investment:
With no related allowance recorded	0	8
With an allowance recorded	15	9
Average recorded investment	15	17
Interest income recognized:
With an allowance recorded	$ 0	$ 0