Bank segment - Credit risk profile - payment activity and assigned grades (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Credit risk profile by internally assigned grade for loans
Current year	$ 909,732	$ 1,325,112
One year before current year	1,233,032	934,584
Two years before current year	838,428	367,452
Three years before current year	307,911	236,305
Four years before current year	168,723	217,965
Prior	1,140,557	1,119,478
Revolving	1,046,278	958,710
Converted to term loans	62,517	61,598
Total	5,707,178	5,221,204
Real estate
Credit risk profile by internally assigned grade for loans
Total	4,786,697	4,313,934
Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current year	305,656	791,758
One year before current year	761,490	461,683
Two years before current year	428,355	136,332
Three years before current year	115,625	65,230
Four years before current year	54,232	124,994
Prior	727,422	719,215
Revolving	0	0
Converted to term loans	0	0
Total	2,392,780	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	925,003	795,668
Converted to term loans	42,150	39,995
Total	967,153	835,663
Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current year	5,516	10,572
One year before current year	9,263	6,794
Two years before current year	5,410	1,116
Three years before current year	338	532
Four years before current year	525	267
Prior	487	578
Revolving	0	0
Converted to term loans	0	0
Total	21,539	19,859
Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current year	6,028	7,856
One year before current year	11,804	3,019
Two years before current year	2,471	0
Three years before current year	0	0
Four years before current year	0	263
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	20,303	11,138
Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current year	293,602	193,394
One year before current year	191,003	279,455
Two years before current year	301,272	106,188
Three years before current year	104,162	89,219
Four years before current year	60,094	56,174
Prior	341,369	320,950
Revolving	4,235	11,602
Converted to term loans	0	0
Total	1,295,737	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	46,263	43,261
Two years before current year	9,570	0
Three years before current year	0	11,342
Four years before current year	11,342	0
Prior	0	0
Revolving	22,010	19,337
Converted to term loans	0	0
Total	89,185	91,080
Consumer
Credit risk profile by internally assigned grade for loans
Current year	153,299	37,838
One year before current year	25,409	15,889
Two years before current year	8,017	30,679
Three years before current year	12,187	11,506
Four years before current year	1,626	352
Prior	167	238
Revolving	11,229	13,044
Converted to term loans	4,810	4,420
Total	216,744	113,966
Commercial
Credit risk profile by internally assigned grade for loans
Current year	145,631	266,554
One year before current year	187,800	124,483
Two years before current year	83,333	93,137
Three years before current year	75,599	58,476
Four years before current year	40,904	35,915
Prior	71,112	78,497
Revolving	83,801	119,059
Converted to term loans	15,557	17,183
Total	703,737	793,304
Pass | Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current year	293,602	173,794
One year before current year	179,753	275,242
Two years before current year	297,137	49,317
Three years before current year	51,953	56,490
Four years before current year	57,857	33,581
Prior	297,949	259,583
Revolving	4,235	11,602
Converted to term loans	0	0
Total	1,182,486	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	46,263	43,261
Two years before current year	9,570	0
Three years before current year	0	11,342
Four years before current year	11,342	0
Prior	0	0
Revolving	22,010	19,337
Converted to term loans	0	0
Total	89,185	91,080
Pass | Commercial
Credit risk profile by internally assigned grade for loans
Current year	145,209	266,087
One year before current year	185,304	96,963
Two years before current year	82,895	79,329
Three years before current year	68,730	56,497
Four years before current year	39,524	31,019
Prior	65,509	66,570
Revolving	75,669	96,673
Converted to term loans	14,430	15,510
Total	677,270	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	11,250	3,529
Two years before current year	3,467	42,935
Three years before current year	40,838	30,870
Four years before current year	415	20,788
Prior	27,202	32,824
Revolving	0	0
Converted to term loans	0	0
Total	83,172	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	0	27,336
Two years before current year	295	10,071
Three years before current year	6,103	202
Four years before current year	25	439
Prior	784	8,966
Revolving	3,750	15,303
Converted to term loans	10	18
Total	10,967	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	668	13,936
Three years before current year	11,371	1,859
Four years before current year	1,822	1,805
Prior	16,218	28,543
Revolving	0	0
Converted to term loans	0	0
Total	30,079	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	422	427
One year before current year	2,496	184
Two years before current year	143	3,737
Three years before current year	766	1,777
Four years before current year	1,355	4,457
Prior	4,819	2,961
Revolving	4,382	7,083
Converted to term loans	1,117	1,655
Total	15,500	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	305,656	791,758
One year before current year	761,490	461,683
Two years before current year	428,088	133,345
Three years before current year	115,625	64,421
Four years before current year	53,423	124,994
Prior	720,572	712,452
Revolving	0	0
Converted to term loans	0	0
Total	2,384,854	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	924,228	794,518
Converted to term loans	41,514	39,116
Total	965,742	833,634
Current | Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current year	5,516	10,572
One year before current year	9,263	6,794
Two years before current year	5,410	1,116
Three years before current year	338	532
Four years before current year	525	267
Prior	390	181
Revolving	0	0
Converted to term loans	0	0
Total	21,442	19,462
Current | Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current year	6,028	7,856
One year before current year	11,804	3,019
Two years before current year	2,471	0
Three years before current year	0	0
Four years before current year	0	263
Prior	0	0
Revolving	0	0
Converted to term loans	0	0
Total	20,303	11,138
Current | Consumer
Credit risk profile by internally assigned grade for loans
Current year	152,156	37,563
One year before current year	24,939	15,488
Two years before current year	7,779	29,383
Three years before current year	11,509	10,897
Four years before current year	1,487	302
Prior	167	238
Revolving	11,097	12,740
Converted to term loans	4,536	4,157
Total	213,670	110,768
30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	3,674	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	1,389	2,210
Revolving	0	0
Converted to term loans	0	0
Total	1,389	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	242	296
Converted to term loans	130	313
Total	372	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	786	202
One year before current year	181	181
Two years before current year	119	517
Three years before current year	303	234
Four years before current year	43	15
Prior	0	0
Revolving	41	156
Converted to term loans	74	70
Total	1,547	1,375
30-59 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	366	700
60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	2,962	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	2,040	1,468
Revolving	0	0
Converted to term loans	0	0
Total	2,040	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	43	70
Total	149	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	229	59
One year before current year	111	127
Two years before current year	50	392
Three years before current year	162	183
Four years before current year	35	8
Prior	0	0
Revolving	23	7
Converted to term loans	53	106
Total	663	882
60-89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	110	313
Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	8,448	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	267	2,987
Three years before current year	0	0
Four years before current year	809	0
Prior	3,421	3,085
Revolving	0	0
Converted to term loans	0	0
Total	4,497	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	427	838
Converted to term loans	463	496
Total	890	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	97	397
Revolving	0	0
Converted to term loans	0	0
Total	97	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	128	14
One year before current year	178	93
Two years before current year	69	387
Three years before current year	213	192
Four years before current year	61	27
Prior	0	0
Revolving	68	141
Converted to term loans	147	87
Total	864	941
Greater than 89 days past due | Commercial
Credit risk profile by internally assigned grade for loans
Total	$ 2,100	$ 48