Bank segment - Credit risk profile - payment activity and assigned grades (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Credit risk profile by internally assigned grade for loans
Current Year	$ 186,653	$ 1,325,112
One Year before Current Year	1,282,228	934,584
Two Years before Current Year	894,415	367,452
Three Years before Current Year	343,354	236,305
Four Years before Current Year	204,145	217,965
Prior	1,261,115	1,119,478
Revolving	960,153	958,710
Converted to term loans	61,197	61,598
Total	5,193,260	5,221,204
Real estate
Credit risk profile by internally assigned grade for loans
Total	4,368,723	4,313,934
Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	77,374	791,758
One Year before Current Year	779,764	461,683
Two Years before Current Year	448,738	136,332
Three Years before Current Year	125,136	65,230
Four Years before Current Year	59,776	124,994
Prior	788,883	719,215
Revolving	0	0
Converted to term loans	0	0
Total	2,279,671	2,299,212
Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	804,781	795,668
Converted to term loans	40,490	39,995
Total	845,271	835,663
Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	2,703	10,572
One Year before Current Year	10,550	6,794
Two Years before Current Year	6,725	1,116
Three Years before Current Year	958	532
Four Years before Current Year	530	267
Prior	843	578
Revolving	0	0
Converted to term loans	0	0
Total	22,309	19,859
Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	2,423	7,856
One Year before Current Year	10,493	3,019
Two Years before Current Year	2,336	0
Three Years before Current Year	0	0
Four Years before Current Year	0	263
Prior	256	0
Revolving	0	0
Converted to term loans	0	0
Total	15,508	11,138
Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	72,390	193,394
One Year before Current Year	191,141	279,455
Two Years before Current Year	296,719	106,188
Three Years before Current Year	106,169	89,219
Four Years before Current Year	77,736	56,174
Prior	367,242	320,950
Revolving	4,235	11,602
Converted to term loans	0	0
Total	1,115,632	1,056,982
Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	119	17,140
One Year before Current Year	22,614	43,261
Two Years before Current Year	32,846	0
Three Years before Current Year	0	11,342
Four Years before Current Year	11,341	0
Prior	0	0
Revolving	23,412	19,337
Converted to term loans	0	0
Total	90,332	91,080
Consumer
Credit risk profile by internally assigned grade for loans
Current Year	23,123	37,838
One Year before Current Year	33,051	15,889
Two Years before Current Year	12,939	30,679
Three Years before Current Year	23,200	11,506
Four Years before Current Year	6,901	352
Prior	333	238
Revolving	12,116	13,044
Converted to term loans	4,427	4,420
Total	116,090	113,966
Commercial
Credit risk profile by internally assigned grade for loans
Current Year	8,521	266,554
One Year before Current Year	234,615	124,483
Two Years before Current Year	94,112	93,137
Three Years before Current Year	87,891	58,476
Four Years before Current Year	47,861	35,915
Prior	103,558	78,497
Revolving	115,609	119,059
Converted to term loans	16,280	17,183
Total	708,447	793,304
Pass | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	72,390	173,794
One Year before Current Year	171,541	275,242
Two Years before Current Year	292,533	49,317
Three Years before Current Year	53,006	56,490
Four Years before Current Year	61,639	33,581
Prior	296,669	259,583
Revolving	4,235	11,602
Converted to term loans	0	0
Total	952,013	859,609
Pass | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	119	17,140
One Year before Current Year	22,614	43,261
Two Years before Current Year	32,846	0
Three Years before Current Year	0	11,342
Four Years before Current Year	11,341	0
Prior	0	0
Revolving	23,412	19,337
Converted to term loans	0	0
Total	90,332	91,080
Pass | Commercial
Credit risk profile by internally assigned grade for loans
Current Year	8,521	266,087
One Year before Current Year	234,161	96,963
Two Years before Current Year	83,927	79,329
Three Years before Current Year	75,241	56,497
Four Years before Current Year	46,058	31,019
Prior	89,119	66,570
Revolving	89,919	96,673
Converted to term loans	14,951	15,510
Total	641,897	708,648
Special Mention | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	0	19,600
One Year before Current Year	19,600	3,529
Two Years before Current Year	3,508	42,935
Three Years before Current Year	41,925	30,870
Four Years before Current Year	14,250	20,788
Prior	43,372	32,824
Revolving	0	0
Converted to term loans	0	0
Total	122,655	150,546
Special Mention | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Special Mention | Commercial
Credit risk profile by internally assigned grade for loans
Current Year	0	40
One Year before Current Year	31	27,336
Two Years before Current Year	10,012	10,071
Three Years before Current Year	9,540	202
Four Years before Current Year	117	439
Prior	7,680	8,966
Revolving	18,364	15,303
Converted to term loans	17	18
Total	45,761	62,375
Substandard | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	684
Two Years before Current Year	678	13,936
Three Years before Current Year	11,238	1,859
Four Years before Current Year	1,847	1,805
Prior	27,201	28,543
Revolving	0	0
Converted to term loans	0	0
Total	40,964	46,827
Substandard | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Substandard | Commercial
Credit risk profile by internally assigned grade for loans
Current Year	0	427
One Year before Current Year	423	184
Two Years before Current Year	173	3,737
Three Years before Current Year	3,110	1,777
Four Years before Current Year	1,686	4,457
Prior	6,759	2,961
Revolving	7,326	7,083
Converted to term loans	1,312	1,655
Total	20,789	22,281
Doubtful | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Doubtful | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Doubtful | Commercial
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Current | Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	77,374	791,758
One Year before Current Year	779,764	461,683
Two Years before Current Year	448,738	133,345
Three Years before Current Year	125,136	64,421
Four Years before Current Year	58,967	124,994
Prior	781,055	712,452
Revolving	0	0
Converted to term loans	0	0
Total	2,271,034	2,288,653
Current | Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	803,515	794,518
Converted to term loans	39,683	39,116
Total	843,198	833,634
Current | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	2,703	10,572
One Year before Current Year	10,550	6,794
Two Years before Current Year	6,725	1,116
Three Years before Current Year	958	532
Four Years before Current Year	530	267
Prior	446	181
Revolving	0	0
Converted to term loans	0	0
Total	21,912	19,462
Current | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	2,423	7,856
One Year before Current Year	10,493	3,019
Two Years before Current Year	2,336	0
Three Years before Current Year	0	0
Four Years before Current Year	0	263
Prior	256	0
Revolving	0	0
Converted to term loans	0	0
Total	15,508	11,138
Current | Consumer
Credit risk profile by internally assigned grade for loans
Current Year	22,938	37,563
One Year before Current Year	32,765	15,488
Two Years before Current Year	12,643	29,383
Three Years before Current Year	22,292	10,897
Four Years before Current Year	6,434	302
Prior	318	238
Revolving	11,886	12,740
Converted to term loans	4,163	4,157
Total	113,439	110,768
30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	4,267	5,703
30-59 days past due | Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	809
Four Years before Current Year	0	0
Prior	1,920	2,210
Revolving	0	0
Converted to term loans	0	0
Total	1,920	3,019
30-59 days past due | Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	457	296
Converted to term loans	512	313
Total	969	609
30-59 days past due | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
30-59 days past due | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
30-59 days past due | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Total	0	0
30-59 days past due | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Total	0	0
30-59 days past due | Consumer
Credit risk profile by internally assigned grade for loans
Current Year	185	202
One Year before Current Year	187	181
Two Years before Current Year	126	517
Three Years before Current Year	377	234
Four Years before Current Year	170	15
Prior	2	0
Revolving	96	156
Converted to term loans	35	70
Total	1,178	1,375
30-59 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	200	700
60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	3,238	2,749
60-89 days past due | Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	2,414	1,468
Revolving	0	0
Converted to term loans	0	0
Total	2,414	1,468
60-89 days past due | Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	64	16
Converted to term loans	0	70
Total	64	86
60-89 days past due | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
60-89 days past due | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
60-89 days past due | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Total	0	0
60-89 days past due | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Total	0	0
60-89 days past due | Consumer
Credit risk profile by internally assigned grade for loans
Current Year	0	59
One Year before Current Year	56	127
Two Years before Current Year	115	392
Three Years before Current Year	278	183
Four Years before Current Year	97	8
Prior	4	0
Revolving	23	7
Converted to term loans	48	106
Total	621	882
60-89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	139	313
Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	6,632	8,792
Greater than 89 days past due | Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	2,987
Three Years before Current Year	0	0
Four Years before Current Year	809	0
Prior	3,494	3,085
Revolving	0	0
Converted to term loans	0	0
Total	4,303	6,072
Greater than 89 days past due | Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	745	838
Converted to term loans	295	496
Total	1,040	1,334
Greater than 89 days past due | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	397	397
Revolving	0	0
Converted to term loans	0	0
Total	397	397
Greater than 89 days past due | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	0	0
One Year before Current Year	0	0
Two Years before Current Year	0	0
Three Years before Current Year	0	0
Four Years before Current Year	0	0
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	0	0
Greater than 89 days past due | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Total	0	0
Greater than 89 days past due | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Total	0	0
Greater than 89 days past due | Consumer
Credit risk profile by internally assigned grade for loans
Current Year	0	14
One Year before Current Year	43	93
Two Years before Current Year	55	387
Three Years before Current Year	253	192
Four Years before Current Year	200	27
Prior	9	0
Revolving	111	141
Converted to term loans	181	87
Total	852	941
Greater than 89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	$ 40	$ 48