Bank segment - Principal balance of impaired loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2019
Recorded investment:
With no related allowance recorded		$ 14,037
With an allowance recorded		26,700
Recorded investment		40,737
Unpaid principal balance:
With no related allowance recorded		15,123
With an allowance recorded		26,762
Unpaid principal balance		41,885
Related Allowance		2,691
Average recorded investment:
With no related allowance recorded	$ 16,565
With an allowance recorded	25,959
Average recorded investment	42,524
Interest income recognized:
With no related allowance recorded	198
With an allowance recorded	250
Interest income recognized	448
Residential 1-4 family
Recorded investment:
With no related allowance recorded		6,817
With an allowance recorded		8,783
Recorded investment		15,600
Unpaid principal balance:
With no related allowance recorded		7,207
With an allowance recorded		8,835
Unpaid principal balance		16,042
Related Allowance		898
Average recorded investment:
With no related allowance recorded	7,991
With an allowance recorded	8,394
Average recorded investment	16,385
Interest income recognized:
With no related allowance recorded	160
With an allowance recorded	83
Interest income recognized	243
Commercial real estate
Recorded investment:
With no related allowance recorded		195
With an allowance recorded		853
Recorded investment		1,048
Unpaid principal balance:
With no related allowance recorded		200
With an allowance recorded		853
Unpaid principal balance		1,053
Related Allowance		2
Average recorded investment:
With no related allowance recorded	0
With an allowance recorded	906
Average recorded investment	906
Interest income recognized:
With no related allowance recorded	0
With an allowance recorded	10
Interest income recognized	10
Home equity line of credit
Recorded investment:
With no related allowance recorded		1,984
With an allowance recorded		10,089
Recorded investment		12,073
Unpaid principal balance:
With no related allowance recorded		2,135
With an allowance recorded		10,099
Unpaid principal balance		12,234
Related Allowance		322
Average recorded investment:
With no related allowance recorded	2,534
With an allowance recorded	11,823
Average recorded investment	14,357
Interest income recognized:
With no related allowance recorded	12
With an allowance recorded	130
Interest income recognized	142
Residential land
Recorded investment:
With no related allowance recorded		3,091
With an allowance recorded		0
Recorded investment		3,091
Unpaid principal balance:
With no related allowance recorded		3,294
With an allowance recorded		0
Unpaid principal balance		3,294
Related Allowance		0
Average recorded investment:
With no related allowance recorded	2,036
With an allowance recorded	29
Average recorded investment	2,065
Interest income recognized:
With no related allowance recorded	26
With an allowance recorded	0
Interest income recognized	26
Commercial construction
Recorded investment:
With no related allowance recorded		0
With an allowance recorded		0
Recorded investment		0
Unpaid principal balance:
With no related allowance recorded		0
With an allowance recorded		0
Unpaid principal balance		0
Related Allowance		0
Average recorded investment:
With no related allowance recorded	0
With an allowance recorded	0
Average recorded investment	0
Interest income recognized:
With no related allowance recorded	0
With an allowance recorded	0
Interest income recognized	0
Residential construction
Recorded investment:
With no related allowance recorded		0
With an allowance recorded		0
Recorded investment		0
Unpaid principal balance:
With no related allowance recorded		0
With an allowance recorded		0
Unpaid principal balance		0
Related Allowance		0
Average recorded investment:
With no related allowance recorded	0
With an allowance recorded	0
Average recorded investment	0
Interest income recognized:
With no related allowance recorded	0
With an allowance recorded	0
Interest income recognized	0
Commercial loans
Recorded investment:
With no related allowance recorded		1,948
With an allowance recorded		6,470
Recorded investment		8,418
Unpaid principal balance:
With no related allowance recorded		2,285
With an allowance recorded		6,470
Unpaid principal balance		8,755
Related Allowance		1,015
Average recorded investment:
With no related allowance recorded	3,973
With an allowance recorded	4,750
Average recorded investment	8,723
Interest income recognized:
With no related allowance recorded	0
With an allowance recorded	26
Interest income recognized	26
Consumer loans
Recorded investment:
With no related allowance recorded		2
With an allowance recorded		505
Recorded investment		507
Unpaid principal balance:
With no related allowance recorded		2
With an allowance recorded		505
Unpaid principal balance		507
Related Allowance		$ 454
Average recorded investment:
With no related allowance recorded	31
With an allowance recorded	57
Average recorded investment	88
Interest income recognized:
With no related allowance recorded	0
With an allowance recorded	1
Interest income recognized	$ 1