Bank segment - Credit risk profile - payment activity and assigned grades (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Credit risk profile by internally assigned grade for loans
March 31, 2020	$ 221,299
December 31, 2019	723,689
December 31, 2018	530,366
December 31, 2017	433,312
December 31, 2016	424,943
Prior	1,474,439
Revolving loans	1,318,782
Revolving loans converted to term loans	53,548
Total	5,180,378
Residential 1-4 family
Credit risk profile by internally assigned grade for loans
March 31, 2020	72,453
December 31, 2019	292,483
December 31, 2018	194,702
December 31, 2017	276,506
December 31, 2016	230,723
Prior	1,095,027
Revolving loans	0
Revolving loans converted to term loans	0
Total	2,161,894
Residential 1-4 family | Current
Credit risk profile by internally assigned grade for loans
March 31, 2020	72,453
December 31, 2019	292,483
December 31, 2018	194,702
December 31, 2017	276,153
December 31, 2016	230,719
Prior	1,089,697
Revolving loans	0
Revolving loans converted to term loans	0
Total	2,156,207
Residential 1-4 family | 30-59 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	4
Prior	2,777
Revolving loans	0
Revolving loans converted to term loans	0
Total	2,781
Residential 1-4 family | 60-89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	1,630
Revolving loans	0
Revolving loans converted to term loans	0
Total	1,630
Residential 1-4 family | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	353
December 31, 2016	0
Prior	923
Revolving loans	0
Revolving loans converted to term loans	0
Total	1,276
Home equity line of credit
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	1,064,131
Revolving loans converted to term loans	31,546
Total	1,095,677
Conversion of debt	1,800
Home equity line of credit | Current
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	1,062,097
Revolving loans converted to term loans	30,327
Total	1,092,424
Home equity line of credit | 30-59 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	633
Revolving loans converted to term loans	592
Total	1,225
Home equity line of credit | 60-89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	26
Revolving loans converted to term loans	198
Total	224
Home equity line of credit | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	1,375
Revolving loans converted to term loans	429
Total	1,804
Residential land
Credit risk profile by internally assigned grade for loans
March 31, 2020	305
December 31, 2019	5,402
December 31, 2018	2,024
December 31, 2017	2,954
December 31, 2016	22
Prior	3,013
Revolving loans	0
Revolving loans converted to term loans	0
Total	13,720
Residential land | Current
Credit risk profile by internally assigned grade for loans
March 31, 2020	305
December 31, 2019	5,402
December 31, 2018	2,024
December 31, 2017	2,954
December 31, 2016	22
Prior	3,013
Revolving loans	0
Revolving loans converted to term loans	0
Total	13,720
Residential land | 30-59 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Residential land | 60-89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Residential land | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Residential construction
Credit risk profile by internally assigned grade for loans
March 31, 2020	1,069
December 31, 2019	5,410
December 31, 2018	682
December 31, 2017	2,029
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	9,190
Residential construction | Current
Credit risk profile by internally assigned grade for loans
March 31, 2020	1,069
December 31, 2019	5,410
December 31, 2018	682
December 31, 2017	2,029
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	9,190
Residential construction | 30-59 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Residential construction | 60-89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Residential construction | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Consumer
Credit risk profile by internally assigned grade for loans
March 31, 2020	23,454
December 31, 2019	101,328
December 31, 2018	66,634
December 31, 2017	20,392
December 31, 2016	3,297
Prior	601
Revolving loans	26,823
Revolving loans converted to term loans	3,224
Total	245,753
Conversion of debt	1,000
Consumer | Current
Credit risk profile by internally assigned grade for loans
March 31, 2020	23,191
December 31, 2019	98,543
December 31, 2018	62,983
December 31, 2017	19,183
December 31, 2016	3,099
Prior	600
Revolving loans	26,079
Revolving loans converted to term loans	3,001
Total	236,679
Consumer | 30-59 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	263
December 31, 2019	1,180
December 31, 2018	1,311
December 31, 2017	486
December 31, 2016	82
Prior	0
Revolving loans	258
Revolving loans converted to term loans	92
Total	3,672
Consumer | 60-89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	843
December 31, 2018	1,225
December 31, 2017	337
December 31, 2016	43
Prior	0
Revolving loans	128
Revolving loans converted to term loans	40
Total	2,616
Consumer | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	762
December 31, 2018	1,115
December 31, 2017	386
December 31, 2016	73
Prior	1
Revolving loans	358
Revolving loans converted to term loans	91
Total	2,786
Commercial real estate
Credit risk profile by internally assigned grade for loans
March 31, 2020	90,614
December 31, 2019	119,868
December 31, 2018	134,627
December 31, 2017	66,094
December 31, 2016	130,056
Prior	293,419
Revolving loans	17,442
Revolving loans converted to term loans	0
Total	852,120
Commercial real estate | Pass
Credit risk profile by internally assigned grade for loans
March 31, 2020	87,054
December 31, 2019	119,868
December 31, 2018	128,356
December 31, 2017	60,786
December 31, 2016	122,917
Prior	233,064
Revolving loans	17,442
Revolving loans converted to term loans	0
Total	769,487
Commercial real estate | Special Mention
Credit risk profile by internally assigned grade for loans
March 31, 2020	3,560
December 31, 2019	0
December 31, 2018	4,331
December 31, 2017	4,700
December 31, 2016	3,457
Prior	3,421
Revolving loans	0
Revolving loans converted to term loans	0
Total	19,469
Commercial real estate | Substandard
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	1,940
December 31, 2017	608
December 31, 2016	3,682
Prior	56,934
Revolving loans	0
Revolving loans converted to term loans	0
Total	63,164
Commercial real estate | Doubtful
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Commercial construction
Credit risk profile by internally assigned grade for loans
March 31, 2020	3,139
December 31, 2019	6,889
December 31, 2018	25,925
December 31, 2017	17,771
December 31, 2016	2,068
Prior	2,289
Revolving loans	21,296
Revolving loans converted to term loans	0
Total	79,377
Commercial construction | Pass
Credit risk profile by internally assigned grade for loans
March 31, 2020	3,139
December 31, 2019	6,889
December 31, 2018	25,925
December 31, 2017	17,771
December 31, 2016	2,068
Prior	0
Revolving loans	21,296
Revolving loans converted to term loans	0
Total	77,088
Commercial construction | Special Mention
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Commercial construction | Substandard
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	2,289
Revolving loans	0
Revolving loans converted to term loans	0
Total	2,289
Commercial construction | Doubtful
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	0
Commercial loans
Credit risk profile by internally assigned grade for loans
March 31, 2020	30,265
December 31, 2019	192,309
December 31, 2018	105,772
December 31, 2017	47,566
December 31, 2016	58,777
Prior	80,090
Revolving loans	189,090
Revolving loans converted to term loans	18,778
Total	722,647
Conversion of debt	2,000
Commercial loans | Pass
Credit risk profile by internally assigned grade for loans
March 31, 2020	29,594
December 31, 2019	180,576
December 31, 2018	103,190
December 31, 2017	40,697
December 31, 2016	35,704
Prior	66,885
Revolving loans	184,425
Revolving loans converted to term loans	17,315
Total	658,386
Commercial loans | Special Mention
Credit risk profile by internally assigned grade for loans
March 31, 2020	473
December 31, 2019	6,625
December 31, 2018	2,252
December 31, 2017	5,219
December 31, 2016	18,782
Prior	9,651
Revolving loans	2,261
Revolving loans converted to term loans	0
Total	45,263
Commercial loans | Substandard
Credit risk profile by internally assigned grade for loans
March 31, 2020	198
December 31, 2019	5,108
December 31, 2018	330
December 31, 2017	1,650
December 31, 2016	4,291
Prior	3,554
Revolving loans	2,404
Revolving loans converted to term loans	1,463
Total	18,998
Commercial loans | Doubtful
Credit risk profile by internally assigned grade for loans
March 31, 2020	0
December 31, 2019	0
December 31, 2018	0
December 31, 2017	0
December 31, 2016	0
Prior	0
Revolving loans	0
Revolving loans converted to term loans	0
Total	$ 0