Bank segment - Credit Risk Profile - Payment Activity and Assigned Grades (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Credit risk profile by internally assigned grade for loans
Current year	$ 470,984		$ 470,984		$ 1,296,473
One year before current year	1,222,693		1,222,693		1,220,751
Two years before current year	1,148,475		1,148,475		808,953
Three years before current year	757,370		757,370		296,592
Four years before current year	247,641		247,641		164,815
Prior	1,140,981		1,140,981		1,077,705
Revolving	1,163,634		1,163,634		1,077,634
Converted to term loans	69,324		69,324		62,098
Total	6,221,102		6,221,102		6,005,021
Gross charge-offs	2,792	$ 1,646	9,417	$ 4,721
30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	7,326		7,326		5,959
60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	3,347		3,347		2,343
Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	4,285		4,285		5,624
Real estate
Credit risk profile by internally assigned grade for loans
Total	5,205,698		5,205,698		4,970,621
Real estate | Residential 1-4 family
Credit risk profile by internally assigned grade for loans
Current year	199,880		199,880		432,707
One year before current year	414,053		414,053		755,056
Two years before current year	741,401		741,401		423,723
Three years before current year	405,819		405,819		113,096
Four years before current year	107,566		107,566		53,117
Prior	697,581		697,581		701,938
Revolving	0		0		0
Converted to term loans	0		0		0
Total	2,566,300		2,566,300		2,479,637
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			990
Charge offs revolving loans			0
Charge offs converted to term loans			0
Gross charge-offs	0	0	990	0
Real estate | Residential 1-4 family | Current
Credit risk profile by internally assigned grade for loans
Current year	199,880		199,880		432,707
One year before current year	414,053		414,053		755,056
Two years before current year	741,401		741,401		423,455
Three years before current year	405,552		405,552		113,096
Four years before current year	107,566		107,566		51,860
Prior	692,167		692,167		698,354
Revolving	0		0		0
Converted to term loans	0		0		0
Total	2,560,619		2,560,619		2,474,528
Real estate | Residential 1-4 family | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	267		267		0
Four years before current year	0		0		448
Prior	2,654		2,654		1,098
Revolving	0		0		0
Converted to term loans	0		0		0
Total	2,921		2,921		1,546
Real estate | Residential 1-4 family | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		268
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	973		973		90
Revolving	0		0		0
Converted to term loans	0		0		0
Total	973		973		358
Real estate | Residential 1-4 family | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		809
Prior	1,787		1,787		2,396
Revolving	0		0		0
Converted to term loans	0		0		0
Total	1,787		1,787		3,205
Real estate | Home equity line of credit
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	977,337		977,337		961,030
Converted to term loans	55,412		55,412		41,875
Total	1,032,749		1,032,749		1,002,905
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			77
Charge offs converted to term loans			283
Gross charge-offs	0	0	360	0
Real estate | Home equity line of credit | Current
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	976,029		976,029		959,131
Converted to term loans	54,579		54,579		40,814
Total	1,030,608		1,030,608		999,945
Real estate | Home equity line of credit | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	463		463		1,103
Converted to term loans	246		246		209
Total	709		709		1,312
Real estate | Home equity line of credit | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	350		350		209
Converted to term loans	321		321		226
Total	671		671		435
Real estate | Home equity line of credit | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	495		495		587
Converted to term loans	266		266		626
Total	761		761		1,213
Real estate | Residential land
Credit risk profile by internally assigned grade for loans
Current year	3,077		3,077		5,245
One year before current year	5,118		5,118		9,010
Two years before current year	7,549		7,549		5,222
Three years before current year	3,518		3,518		203
Four years before current year	0		0		522
Prior	983		983		477
Revolving	0		0		0
Converted to term loans	0		0		0
Total	20,245		20,245		20,679
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			0
Charge offs converted to term loans			0
Gross charge-offs	0	0	0	0
Real estate | Residential land | Current
Credit risk profile by internally assigned grade for loans
Current year	3,077		3,077		5,245
One year before current year	5,118		5,118		9,010
Two years before current year	7,549		7,549		5,222
Three years before current year	3,518		3,518		203
Four years before current year	0		0		522
Prior	983		983		477
Revolving	0		0		0
Converted to term loans	0		0		0
Total	20,245		20,245		20,679
Real estate | Residential land | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Residential land | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Residential land | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Residential construction
Credit risk profile by internally assigned grade for loans
Current year	2,780		2,780		7,986
One year before current year	11,019		11,019		11,624
Two years before current year	3,496		3,496		1,178
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	17,295		17,295		20,788
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			0
Charge offs converted to term loans			0
Gross charge-offs	0	0	0	0
Real estate | Residential construction | Current
Credit risk profile by internally assigned grade for loans
Current year	2,780		2,780		7,986
One year before current year	11,019		11,019		11,624
Two years before current year	3,496		3,496		1,178
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	17,295		17,295		20,788
Real estate | Residential construction | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Residential construction | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Residential construction | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Commercial real estate
Credit risk profile by internally assigned grade for loans
Current year	86,673		86,673		390,206
One year before current year	390,352		390,352		188,380
Two years before current year	189,888		189,888		287,432
Three years before current year	269,189		269,189		103,322
Four years before current year	91,612		91,612		63,084
Prior	357,374		357,374		317,464
Revolving	15,482		15,482		8,235
Converted to term loans	0		0		0
Total	1,400,570		1,400,570		1,358,123
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			0
Charge offs converted to term loans			0
Gross charge-offs	0	0	0	0
Real estate | Commercial real estate | Pass
Credit risk profile by internally assigned grade for loans
Current year	81,287		81,287		390,206
One year before current year	390,352		390,352		177,130
Two years before current year	177,125		177,125		283,321
Three years before current year	265,808		265,808		51,542
Four years before current year	66,112		66,112		63,084
Prior	329,235		329,235		278,280
Revolving	15,482		15,482		8,235
Converted to term loans	0		0		0
Total	1,325,401		1,325,401		1,251,798
Real estate | Commercial real estate | Special Mention
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		11,250
Two years before current year	11,214		11,214		3,446
Three years before current year	3,381		3,381		40,423
Four years before current year	14,452		14,452		0
Prior	22,367		22,367		24,466
Revolving	0		0		0
Converted to term loans	0		0		0
Total	51,414		51,414		79,585
Real estate | Commercial real estate | Substandard
Credit risk profile by internally assigned grade for loans
Current year	5,386		5,386		0
One year before current year	0		0		0
Two years before current year	1,549		1,549		665
Three years before current year	0		0		11,357
Four years before current year	11,048		11,048		0
Prior	5,772		5,772		14,718
Revolving	0		0		0
Converted to term loans	0		0		0
Total	23,755		23,755		26,740
Real estate | Commercial real estate | Doubtful
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Commercial real estate | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		508
Real estate | Commercial real estate | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		217
Real estate | Commercial real estate | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		0
Real estate | Commercial construction
Credit risk profile by internally assigned grade for loans
Current year	10,643		10,643		15,094
One year before current year	21,440		21,440		47,478
Two years before current year	66,143		66,143		44
Three years before current year	356		356		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	69,957		69,957		25,873
Converted to term loans	0		0		0
Total	168,539		168,539		88,489
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			0
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			0
Charge offs converted to term loans			0
Gross charge-offs	0	0	0	0
Real estate | Commercial construction | Pass
Credit risk profile by internally assigned grade for loans
Current year	10,643		10,643		15,094
One year before current year	21,440		21,440		47,478
Two years before current year	66,143		66,143		44
Three years before current year	356		356		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	69,957		69,957		25,873
Converted to term loans	0		0		0
Total	168,539		168,539		88,489
Real estate | Commercial construction | Special Mention
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Commercial construction | Substandard
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Commercial construction | Doubtful
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Real estate | Commercial construction | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		0
Real estate | Commercial construction | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		0
Real estate | Commercial construction | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	0		0		0
Consumer
Credit risk profile by internally assigned grade for loans
Current year	83,841		83,841		202,061
One year before current year	168,293		168,293		21,885
Two years before current year	12,535		12,535		5,733
Three years before current year	2,505		2,505		8,132
Four years before current year	1,137		1,137		604
Prior	225		225		140
Revolving	10,574		10,574		10,956
Converted to term loans	3,836		3,836		5,198
Total	282,946		282,946		254,709
Charge offs current year			850
Charge offs one year prior of origination year			4,637
Charge offs two years prior of origination year			840
Charge offs three years prior of origination year			163
Charge offs four years prior of origination year			363
Charge offs more than five years prior of origination year			39
Charge offs revolving loans			279
Charge offs converted to term loans			387
Gross charge-offs	2,667	1,503	7,558	4,354
Consumer | Current
Credit risk profile by internally assigned grade for loans
Current year	82,282		82,282		199,574
One year before current year	164,693		164,693		21,330
Two years before current year	12,203		12,203		5,543
Three years before current year	2,394		2,394		7,580
Four years before current year	1,010		1,010		527
Prior	222		222		140
Revolving	10,345		10,345		10,810
Converted to term loans	3,413		3,413		4,782
Total	276,562		276,562		250,286
Consumer | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Current year	822		822		1,110
One year before current year	1,882		1,882		287
Two years before current year	122		122		65
Three years before current year	43		43		239
Four years before current year	49		49		30
Prior	1		1		0
Revolving	46		46		81
Converted to term loans	156		156		167
Total	3,121		3,121		1,979
Consumer | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Current year	362		362		756
One year before current year	933		933		163
Two years before current year	108		108		88
Three years before current year	35		35		137
Four years before current year	52		52		19
Prior	0		0		0
Revolving	32		32		45
Converted to term loans	81		81		107
Total	1,603		1,603		1,315
Consumer | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Current year	375		375		621
One year before current year	785		785		105
Two years before current year	102		102		37
Three years before current year	33		33		176
Four years before current year	26		26		28
Prior	2		2		0
Revolving	151		151		20
Converted to term loans	186		186		142
Total	1,660		1,660		1,129
Commercial
Credit risk profile by internally assigned grade for loans
Current year	84,090		84,090		243,174
One year before current year	212,418		212,418		187,318
Two years before current year	127,463		127,463		85,621
Three years before current year	75,983		75,983		71,839
Four years before current year	47,326		47,326		47,488
Prior	84,818		84,818		57,686
Revolving	90,284		90,284		71,540
Converted to term loans	10,076		10,076		15,025
Total	732,458		732,458		779,691
Charge offs current year			0
Charge offs one year prior of origination year			0
Charge offs two years prior of origination year			51
Charge offs three years prior of origination year			0
Charge offs four years prior of origination year			0
Charge offs more than five years prior of origination year			0
Charge offs revolving loans			177
Charge offs converted to term loans			281
Gross charge-offs	125	$ 143	509	$ 367
Commercial | Pass
Credit risk profile by internally assigned grade for loans
Current year	82,145		82,145		239,852
One year before current year	209,364		209,364		185,013
Two years before current year	124,453		124,453		85,220
Three years before current year	75,753		75,753		68,161
Four years before current year	46,291		46,291		46,142
Prior	81,409		81,409		53,192
Revolving	81,627		81,627		60,871
Converted to term loans	9,560		9,560		13,964
Total	710,602		710,602		752,415
Commercial | Special Mention
Credit risk profile by internally assigned grade for loans
Current year	1,945		1,945		0
One year before current year	0		0		0
Two years before current year	970		970		0
Three years before current year	0		0		2,374
Four years before current year	272		272		0
Prior	0		0		645
Revolving	7,151		7,151		9,005
Converted to term loans	0		0		8
Total	10,338		10,338		12,032
Commercial | Substandard
Credit risk profile by internally assigned grade for loans
Current year	0		0		3,322
One year before current year	3,054		3,054		2,305
Two years before current year	2,040		2,040		401
Three years before current year	230		230		1,304
Four years before current year	763		763		1,346
Prior	3,409		3,409		3,849
Revolving	1,506		1,506		1,664
Converted to term loans	516		516		1,053
Total	11,518		11,518		15,244
Commercial | Doubtful
Credit risk profile by internally assigned grade for loans
Current year	0		0		0
One year before current year	0		0		0
Two years before current year	0		0		0
Three years before current year	0		0		0
Four years before current year	0		0		0
Prior	0		0		0
Revolving	0		0		0
Converted to term loans	0		0		0
Total	0		0		0
Commercial | 30-59 days past due
Credit risk profile by internally assigned grade for loans
Total	575		575		614
Commercial | 60-89 days past due
Credit risk profile by internally assigned grade for loans
Total	100		100		18
Commercial | Greater than 89 days past due
Credit risk profile by internally assigned grade for loans
Total	$ 77		$ 77		$ 77