Loans and Allowance for Credit Losses for Loans - Amortized Cost In Those Loan Classes Based on Payment Activity by Origination Year (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 49,355,319	$ 50,210,295		$ 49,355,319
Gross loan charge-offs
Total	48,221		$ 8,918	111,460	$ 52,818
90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	4,780	13,145		4,780
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	340,813	467,178		340,813
Year two, fiscal year before current fiscal year	447,576	1,305,994		447,576
Year three, two years before current fiscal year	1,303,445	1,506,814		1,303,445
Year four, three years before current fiscal year	1,460,418	540,210		1,460,418
Year five, four years before current fiscal year	508,959	439,060		508,959
More than five years before current fiscal year	1,544,126	1,250,931		1,544,126
Revolving Loans Amortized Cost Basis	77,107	57,052		77,107
Revolving Loans Converted to Term Loans	1,635	1,771		1,635
Total	5,684,079	5,569,010		5,684,079
Gross loan charge-offs
Total	0		20	0	169
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,931	2,488		1,931
Residential mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	340,089	467,178		340,089
Year two, fiscal year before current fiscal year	447,576	1,304,026		447,576
Year three, two years before current fiscal year	1,302,396	1,505,133		1,302,396
Year four, three years before current fiscal year	1,459,396	538,853		1,459,396
Year five, four years before current fiscal year	507,022	435,669		507,022
More than five years before current fiscal year	1,528,196	1,244,986		1,528,196
Revolving Loans Amortized Cost Basis	77,107	57,052		77,107
Revolving Loans Converted to Term Loans	1,635	1,771		1,635
Total	5,663,417	5,554,668		5,663,417
Residential mortgage | Non-performing | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	724	0		724
Year two, fiscal year before current fiscal year	0	1,968		0
Year three, two years before current fiscal year	1,049	1,681		1,049
Year four, three years before current fiscal year	1,022	1,357		1,022
Year five, four years before current fiscal year	1,937	3,391		1,937
More than five years before current fiscal year	15,930	5,945		15,930
Revolving Loans Amortized Cost Basis	0	0		0
Revolving Loans Converted to Term Loans		0
Total	20,662	14,342		20,662
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	677,912	541,513		677,912
Year two, fiscal year before current fiscal year	437,723	597,411		437,723
Year three, two years before current fiscal year	462,488	374,145		462,488
Year four, three years before current fiscal year	257,317	127,568		257,317
Year five, four years before current fiscal year	77,417	101,615		77,417
More than five years before current fiscal year	173,919	135,506		173,919
Revolving Loans Amortized Cost Basis	1,351,493	1,538,050		1,351,493
Revolving Loans Converted to Term Loans	31,488	24,887		31,488
Total	3,469,757	3,440,695		3,469,757
Gross loan charge-offs
Total	2,597		$ 1,156	5,668	$ 3,024
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	13,599	40,599		13,599
Year two, fiscal year before current fiscal year	31,397	44,944		31,397
Year three, two years before current fiscal year	40,153	14,961		40,153
Year four, three years before current fiscal year	10,486	4,096		10,486
Year five, four years before current fiscal year	3,455	4,850		3,455
More than five years before current fiscal year	51,909	47,406		51,909
Revolving Loans Amortized Cost Basis	418,884	396,960		418,884
Revolving Loans Converted to Term Loans	11,298	5,336		11,298
Total	581,181	559,152		581,181
Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	650,111	468,242		650,111
Year two, fiscal year before current fiscal year	379,363	532,012		379,363
Year three, two years before current fiscal year	405,817	356,198		405,817
Year four, three years before current fiscal year	244,866	121,750		244,866
Year five, four years before current fiscal year	73,452	86,384		73,452
More than five years before current fiscal year	70,129	34,813		70,129
Revolving Loans Amortized Cost Basis	0	20,227		0
Revolving Loans Converted to Term Loans	0	763		0
Total	1,823,738	1,620,389		1,823,738
Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	14,202	32,672		14,202
Year two, fiscal year before current fiscal year	26,963	20,455		26,963
Year three, two years before current fiscal year	16,518	2,986		16,518
Year four, three years before current fiscal year	1,965	1,722		1,965
Year five, four years before current fiscal year	510	10,381		510
More than five years before current fiscal year	51,881	53,287		51,881
Revolving Loans Amortized Cost Basis	932,609	1,120,863		932,609
Revolving Loans Converted to Term Loans	20,190	18,788		20,190
Total	1,064,838	1,261,154		1,064,838
Consumer loans | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,063	1,088		1,063
Consumer loans | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0		0
Consumer loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total	831	576		831
Consumer loans | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	232	512		232
Consumer loans | Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	13,599	40,599		13,599
Year two, fiscal year before current fiscal year	31,397	44,893		31,397
Year three, two years before current fiscal year	40,102	14,948		40,102
Year four, three years before current fiscal year	10,473	4,096		10,473
Year five, four years before current fiscal year	3,455	4,850		3,455
More than five years before current fiscal year	51,126	46,274		51,126
Revolving Loans Amortized Cost Basis	418,884	396,960		418,884
Revolving Loans Converted to Term Loans	11,253	4,608		11,253
Total	580,289	557,228		580,289
Consumer loans | Performing | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	650,027	468,152		650,027
Year two, fiscal year before current fiscal year	379,091	531,728		379,091
Year three, two years before current fiscal year	405,626	356,144		405,626
Year four, three years before current fiscal year	244,751	121,658		244,751
Year five, four years before current fiscal year	73,367	86,147		73,367
More than five years before current fiscal year	69,827	34,504		69,827
Revolving Loans Amortized Cost Basis	0	20,227		0
Revolving Loans Converted to Term Loans	0	763		0
Total	1,822,689	1,619,323		1,822,689
Consumer loans | Performing | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	14,202	32,662		14,202
Year two, fiscal year before current fiscal year	26,957	20,376		26,957
Year three, two years before current fiscal year	16,451	2,986		16,451
Year four, three years before current fiscal year	1,965	1,722		1,965
Year five, four years before current fiscal year	510	10,381		510
More than five years before current fiscal year	51,843	52,659		51,843
Revolving Loans Amortized Cost Basis	932,609	1,120,863		932,609
Revolving Loans Converted to Term Loans	20,189	18,655		20,189
Total	1,064,726	1,260,304		1,064,726
Consumer loans | Non-performing | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	0		0
Year two, fiscal year before current fiscal year	0	51		0
Year three, two years before current fiscal year	51	13		51
Year four, three years before current fiscal year	13	0		13
Year five, four years before current fiscal year	0	0		0
More than five years before current fiscal year	783	1,132		783
Revolving Loans Amortized Cost Basis	0	0		0
Revolving Loans Converted to Term Loans	45	728		45
Total	892	1,924		892
Consumer loans | Non-performing | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	84	90		84
Year two, fiscal year before current fiscal year	272	284		272
Year three, two years before current fiscal year	191	54		191
Year four, three years before current fiscal year	115	92		115
Year five, four years before current fiscal year	85	237		85
More than five years before current fiscal year	302	309		302
Revolving Loans Amortized Cost Basis	0	0		0
Revolving Loans Converted to Term Loans	0	0		0
Total	1,049	1,066		1,049
Consumer loans | Non-performing | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0	10		0
Year two, fiscal year before current fiscal year	6	79		6
Year three, two years before current fiscal year	67	0		67
Year four, three years before current fiscal year	0	0		0
Year five, four years before current fiscal year	0	0		0
More than five years before current fiscal year	38	628		38
Revolving Loans Amortized Cost Basis	0	0		0
Revolving Loans Converted to Term Loans	1	133		1
Total	$ 112	850		112
Gross loan charge-offs
Gross loan charge-offs
Year one, gross loan charge-offs		296		419
Year two, gross loan charge-offs		903		1,331
Year three, gross loan charge-offs		357		1,254
Year four, gross loan charge-offs		232		740
Year five, gross loan charge-offs		752		437
More than five years gross loan charge-offs		1,921		1,344
Revolving Loans Amortized Cost Basis		31		0
Revolving Loans Converted to Term Loans		0		143
Total		$ 4,492		$ 5,668