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		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 49,922,042		$ 50,210,295
Gross loan charge-offs
Total	24,900	$ 32,573
90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	13,355		13,145
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	91,866		467,178
Year two, fiscal year before current fiscal year	467,697		1,305,994
Year three, two years before current fiscal year	1,320,501		1,506,814
Year four, three years before current fiscal year	1,493,468		540,210
Year five, four years before current fiscal year	528,197		439,060
More than five years before current fiscal year	1,652,313		1,250,931
Revolving Loans Amortized Cost Basis	62,542		57,052
Revolving Loans Converted to Term Loans	1,771		1,771
Total	5,618,355		5,569,010
Gross loan charge-offs
Total	0	0
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	2,884		2,488
Residential mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	91,866		467,178
Year two, fiscal year before current fiscal year	467,697		1,304,026
Year three, two years before current fiscal year	1,316,817		1,505,133
Year four, three years before current fiscal year	1,491,638		538,853
Year five, four years before current fiscal year	526,843		435,669
More than five years before current fiscal year	1,643,947		1,244,986
Revolving Loans Amortized Cost Basis	62,542		57,052
Revolving Loans Converted to Term Loans	1,771		1,771
Total	5,603,121		5,554,668
Residential mortgage | Non-Performing Loans | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		0
Year two, fiscal year before current fiscal year	0		1,968
Year three, two years before current fiscal year	3,684		1,681
Year four, three years before current fiscal year	1,830		1,357
Year five, four years before current fiscal year	1,354		3,391
More than five years before current fiscal year	8,366		5,945
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	15,234		14,342
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	233,508		541,513
Year two, fiscal year before current fiscal year	522,669		597,411
Year three, two years before current fiscal year	555,445		374,145
Year four, three years before current fiscal year	332,201		127,568
Year five, four years before current fiscal year	110,602		101,615
More than five years before current fiscal year	214,275		135,506
Revolving Loans Amortized Cost Basis	1,489,605		1,538,050
Revolving Loans Converted to Term Loans	35,725		24,887
Total	3,494,030		3,440,695
Gross loan charge-offs
Total	1,809	$ 828
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	2,872		40,599
Year two, fiscal year before current fiscal year	27,946		44,944
Year three, two years before current fiscal year	43,441		14,961
Year four, three years before current fiscal year	11,220		4,096
Year five, four years before current fiscal year	4,021		4,850
More than five years before current fiscal year	54,408		47,406
Revolving Loans Amortized Cost Basis	412,170		396,960
Revolving Loans Converted to Term Loans	8,005		5,336
Total	564,083		559,152
Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	225,477		468,242
Year two, fiscal year before current fiscal year	464,233		532,012
Year three, two years before current fiscal year	492,707		356,198
Year four, three years before current fiscal year	318,252		121,750
Year five, four years before current fiscal year	105,305		86,384
More than five years before current fiscal year	94,534		34,813
Revolving Loans Amortized Cost Basis	0		20,227
Revolving Loans Converted to Term Loans	0		763
Total	1,700,508		1,620,389
Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	5,159		32,672
Year two, fiscal year before current fiscal year	30,490		20,455
Year three, two years before current fiscal year	19,297		2,986
Year four, three years before current fiscal year	2,729		1,722
Year five, four years before current fiscal year	1,276		10,381
More than five years before current fiscal year	65,333		53,287
Revolving Loans Amortized Cost Basis	1,077,435		1,120,863
Revolving Loans Converted to Term Loans	27,720		18,788
Total	1,229,439		1,261,154
Consumer loans | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	731		1,088
Consumer loans | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Consumer loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total	535		576
Consumer loans | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	196		512
Consumer loans | Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	2,872		40,599
Year two, fiscal year before current fiscal year	27,946		44,893
Year three, two years before current fiscal year	43,390		14,948
Year four, three years before current fiscal year	11,207		4,096
Year five, four years before current fiscal year	4,021		4,850
More than five years before current fiscal year	53,706		46,274
Revolving Loans Amortized Cost Basis	412,170		396,960
Revolving Loans Converted to Term Loans	7,957		4,608
Total	563,269		557,228
Consumer loans | Performing | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	225,477		468,152
Year two, fiscal year before current fiscal year	464,201		531,728
Year three, two years before current fiscal year	492,460		356,144
Year four, three years before current fiscal year	318,203		121,658
Year five, four years before current fiscal year	105,243		86,147
More than five years before current fiscal year	94,074		34,504
Revolving Loans Amortized Cost Basis	0		20,227
Revolving Loans Converted to Term Loans			763
Total	1,699,658		1,619,323
Consumer loans | Performing | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	5,159		32,662
Year two, fiscal year before current fiscal year	30,490		20,376
Year three, two years before current fiscal year	19,276		2,986
Year four, three years before current fiscal year	2,729		1,722
Year five, four years before current fiscal year	1,276		10,381
More than five years before current fiscal year	64,706		52,659
Revolving Loans Amortized Cost Basis	1,077,435		1,120,863
Revolving Loans Converted to Term Loans	27,719		18,655
Total	1,228,790		1,260,304
Consumer loans | Non-Performing Loans | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		0
Year two, fiscal year before current fiscal year	0		51
Year three, two years before current fiscal year	51		13
Year four, three years before current fiscal year	13		0
Year five, four years before current fiscal year	0		0
More than five years before current fiscal year	702		1,132
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	48		728
Total	814		1,924
Consumer loans | Non-Performing Loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		90
Year two, fiscal year before current fiscal year	32		284
Year three, two years before current fiscal year	247		54
Year four, three years before current fiscal year	49		92
Year five, four years before current fiscal year	62		237
More than five years before current fiscal year	460		309
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	850		1,066
Consumer loans | Non-Performing Loans | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		10
Year two, fiscal year before current fiscal year	0		79
Year three, two years before current fiscal year	21		0
Year four, three years before current fiscal year	0		0
Year five, four years before current fiscal year	0		0
More than five years before current fiscal year	627		628
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	1		133
Total	649		850
Gross loan charge-offs
Gross loan charge-offs
Year one, gross loan charge-offs	0		296
Year two, gross loan charge-offs	391		903
Year three, gross loan charge-offs	494		357
Year four, gross loan charge-offs	269		232
Year five, gross loan charge-offs	198		752
More than five years gross loan charge-offs	433		1,921
Revolving Loans Amortized Cost Basis	0		31
Revolving Loans Converted to Term Loans	24		0
Total	$ 1,809		$ 4,492