Bank segment - Credit risk profile - payment activity and assigned grades (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Credit risk profile by internally assigned grade for loans
Current Year	$ 529,281	$ 1,325,112
One Year before Current Year	1,227,458	934,584
Two Years before Current Year	885,052	367,452
Three Years before Current Year	325,970	236,305
Four Years before Current Year	197,738	217,965
Prior	1,193,931	1,119,478
Revolving	1,017,811	958,710
Converted to term loans	62,105	61,598
Total	5,439,346	5,221,204
Real estate
Credit risk profile by internally assigned grade for loans
Total	4,630,231	4,313,934
Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current Year	176,333	791,758
One Year before Current Year	768,123	461,683
Two Years before Current Year	438,483	136,332
Three Years before Current Year	119,720	65,230
Four Years before Current Year	57,731	124,994
Prior	749,651	719,215
Revolving	0	0
Converted to term loans	0	0
Total	2,310,041	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	882,144	795,668
Converted to term loans	41,832	39,995
Total	923,976	835,663
Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	4,290	10,572
One Year before Current Year	9,861	6,794
Two Years before Current Year	5,410	1,116
Three Years before Current Year	958	532
Four Years before Current Year	527	267
Prior	489	578
Revolving	0	0
Converted to term loans	0	0
Total	21,535	19,859
Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	5,614	7,856
One Year before Current Year	11,071	3,019
Two Years before Current Year	2,297	0
Three Years before Current Year	0	0
Four Years before Current Year	0	263
Prior	248	0
Revolving	0	0
Converted to term loans	0	0
Total	19,230	11,138
Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	229,603	193,394
One Year before Current Year	191,405	279,455
Two Years before Current Year	305,523	106,188
Three Years before Current Year	105,040	89,219
Four Years before Current Year	77,188	56,174
Prior	348,395	320,950
Revolving	4,235	11,602
Converted to term loans	0	0
Total	1,261,389	1,056,982
Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	0	17,140
One Year before Current Year	35,982	43,261
Two Years before Current Year	25,123	0
Three Years before Current Year	0	11,342
Four Years before Current Year	11,341	0
Prior	0	0
Revolving	21,614	19,337
Converted to term loans	0	0
Total	94,060	91,080
Consumer
Credit risk profile by internally assigned grade for loans
Current Year	71,858	37,838
One Year before Current Year	28,947	15,889
Two Years before Current Year	10,422	30,679
Three Years before Current Year	17,271	11,506
Four Years before Current Year	3,665	352
Prior	200	238
Revolving	11,752	13,044
Converted to term loans	4,522	4,420
Total	148,637	113,966
Commercial
Credit risk profile by internally assigned grade for loans
Current Year	41,583	266,554
One Year before Current Year	182,069	124,483
Two Years before Current Year	97,794	93,137
Three Years before Current Year	82,981	58,476
Four Years before Current Year	47,286	35,915
Prior	94,948	78,497
Revolving	98,066	119,059
Converted to term loans	15,751	17,183
Total	660,478	793,304
Pass | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current Year	229,603	173,794
One Year before Current Year	171,805	275,242
Two Years before Current Year	301,360	49,317
Three Years before Current Year	52,361	56,490
Four Years before Current Year	61,179	33,581
Prior	289,835	259,583
Revolving	4,235	11,602
Converted to term loans	0	0
Total	1,110,378	859,609
Pass | Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current Year	0	17,140
One Year before Current Year	35,982	43,261
Two Years before Current Year	25,123	0
Three Years before Current Year	0	11,342
Four Years before Current Year	11,341	0
Prior	0	0
Revolving	21,614	19,337
Converted to term loans	0	0
Total	94,060	91,080
Pass | Commercial
Credit risk profile by internally assigned grade for loans
Current Year	41,268	266,087
One Year before Current Year	181,637	96,963
Two Years before Current Year	87,936	79,329
Three Years before Current Year	74,326	56,497
Four Years before Current Year	45,637	31,019
Prior	87,962	66,570
Revolving	78,344	96,673
Converted to term loans	14,590	15,510
Total	611,700	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	3,488	42,935
Three Years before Current Year	41,235	30,870
Four Years before Current Year	14,174	20,788
Prior	36,958	32,824
Revolving	0	0
Converted to term loans	0	0
Total	115,455	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	23	27,336
Two Years before Current Year	9,702	10,071
Three Years before Current Year	6,533	202
Four Years before Current Year	101	439
Prior	1,011	8,966
Revolving	15,414	15,303
Converted to term loans	14	18
Total	32,798	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	675	13,936
Three Years before Current Year	11,444	1,859
Four Years before Current Year	1,835	1,805
Prior	21,602	28,543
Revolving	0	0
Converted to term loans	0	0
Total	35,556	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	315	427
One Year before Current Year	409	184
Two Years before Current Year	156	3,737
Three Years before Current Year	2,122	1,777
Four Years before Current Year	1,548	4,457
Prior	5,975	2,961
Revolving	4,308	7,083
Converted to term loans	1,147	1,655
Total	15,980	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	176,333	791,758
One Year before Current Year	768,123	461,683
Two Years before Current Year	437,911	133,345
Three Years before Current Year	119,503	64,421
Four Years before Current Year	56,469	124,994
Prior	742,653	712,452
Revolving	0	0
Converted to term loans	0	0
Total	2,300,992	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	881,505	794,518
Converted to term loans	41,295	39,116
Total	922,800	833,634
Current | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current Year	4,290	10,572
One Year before Current Year	9,861	6,794
Two Years before Current Year	5,410	1,116
Three Years before Current Year	753	532
Four Years before Current Year	527	267
Prior	283	181
Revolving	0	0
Converted to term loans	0	0
Total	21,124	19,462
Current | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current Year	5,614	7,856
One Year before Current Year	11,071	3,019
Two Years before Current Year	2,297	0
Three Years before Current Year	0	0
Four Years before Current Year	0	263
Prior	248	0
Revolving	0	0
Converted to term loans	0	0
Total	19,230	11,138
Current | Consumer
Credit risk profile by internally assigned grade for loans
Current Year	71,436	37,563
One Year before Current Year	28,455	15,488
Two Years before Current Year	10,209	29,383
Three Years before Current Year	16,525	10,897
Four Years before Current Year	3,385	302
Prior	198	238
Revolving	11,509	12,740
Converted to term loans	4,235	4,157
Total	145,952	110,768
30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	6,491	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	572	0
Three Years before Current Year	217	809
Four Years before Current Year	453	0
Prior	3,288	2,210
Revolving	0	0
Converted to term loans	0	0
Total	4,530	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	110	296
Converted to term loans	101	313
Total	211	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	472	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	268	202
One Year before Current Year	224	181
Two Years before Current Year	68	517
Three Years before Current Year	330	234
Four Years before Current Year	82	15
Prior	2	0
Revolving	107	156
Converted to term loans	110	70
Total	1,191	1,375
30-59 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	87	700
60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	2,313	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	637	1,468
Revolving	0	0
Converted to term loans	0	0
Total	637	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	106	16
Converted to term loans	83	70
Total	189	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	109	0
Revolving	0	0
Converted to term loans	0	0
Total	109	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	74	59
One Year before Current Year	109	127
Two Years before Current Year	78	392
Three Years before Current Year	161	183
Four Years before Current Year	91	8
Prior	0	0
Revolving	45	7
Converted to term loans	57	106
Total	615	882
60-89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	763	313
Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	5,848	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	3,073	3,085
Revolving	0	0
Converted to term loans	0	0
Total	3,882	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	423	838
Converted to term loans	353	496
Total	776	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	205	0
Four Years before Current Year	0	0
Prior	97	397
Revolving	0	0
Converted to term loans	0	0
Total	302	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	80	14
One Year before Current Year	159	93
Two Years before Current Year	67	387
Three Years before Current Year	255	192
Four Years before Current Year	107	27
Prior	0	0
Revolving	91	141
Converted to term loans	120	87
Total	879	941
Greater than 89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	$ 9	$ 48