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, 2025	Mar. 31, 2024	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 48,657,128		$ 48,799,711
Gross loan charge-offs
Total	44,019	$ 24,900
90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	7,756		5,889
Residential mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	85,961		428,668
Year two, fiscal year before current fiscal year	427,110		414,299
Year three, two years before current fiscal year	408,983		1,283,554
Year four, three years before current fiscal year	1,277,767		1,422,368
Year five, four years before current fiscal year	1,403,995		499,716
More than five years before current fiscal year	1,954,012		1,506,797
Revolving Loans Amortized Cost Basis	77,898		75,479
Revolving Loans Converted to Term Loans	681		1,635
Total	5,636,407		5,632,516
Gross loan charge-offs
Total	0	0
Residential mortgage | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	6,892		3,533
Residential mortgage | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	85,961		428,138
Year two, fiscal year before current fiscal year	426,158		413,528
Year three, two years before current fiscal year	408,214		1,282,524
Year four, three years before current fiscal year	1,274,491		1,420,835
Year five, four years before current fiscal year	1,402,246		494,430
More than five years before current fiscal year	1,939,273		1,490,512
Revolving Loans Amortized Cost Basis	77,898		75,479
Revolving Loans Converted to Term Loans	0		954
Total	5,614,241		5,606,400
Residential mortgage | Non-performing loan held for sale | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		530
Year two, fiscal year before current fiscal year	952		771
Year three, two years before current fiscal year	769		1,030
Year four, three years before current fiscal year	3,276		1,533
Year five, four years before current fiscal year	1,749		5,286
More than five years before current fiscal year	14,739		16,285
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	681		681
Total	22,166		26,116
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	358,853		901,463
Year two, fiscal year before current fiscal year	823,320		398,761
Year three, two years before current fiscal year	365,940		418,714
Year four, three years before current fiscal year	374,581		223,255
Year five, four years before current fiscal year	190,622		62,967
More than five years before current fiscal year	213,328		165,116
Revolving Loans Amortized Cost Basis	1,407,751		1,395,156
Revolving Loans Converted to Term Loans	21,565		25,405
Total	3,755,960		3,590,837
Gross loan charge-offs
Total	2,140	1,809
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	7,472		22,947
Year two, fiscal year before current fiscal year	22,481		29,493
Year three, two years before current fiscal year	27,297		38,825
Year four, three years before current fiscal year	38,393		10,303
Year five, four years before current fiscal year	9,933		3,340
More than five years before current fiscal year	55,437		51,468
Revolving Loans Amortized Cost Basis	431,436		438,817
Revolving Loans Converted to Term Loans	9,712		9,240
Total	602,161		604,433
Consumer loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	345,515		863,352
Year two, fiscal year before current fiscal year	787,498		343,325
Year three, two years before current fiscal year	308,639		364,041
Year four, three years before current fiscal year	321,261		211,364
Year five, four years before current fiscal year	178,989		59,290
More than five years before current fiscal year	99,325		59,693
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	2,041,227		1,901,065
Consumer loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	5,866		15,164
Year two, fiscal year before current fiscal year	13,341		25,943
Year three, two years before current fiscal year	30,004		15,848
Year four, three years before current fiscal year	14,927		1,588
Year five, four years before current fiscal year	1,700		337
More than five years before current fiscal year	58,566		53,955
Revolving Loans Amortized Cost Basis	976,315		956,339
Revolving Loans Converted to Term Loans	11,853		16,165
Total	1,112,572		1,085,339
Consumer loans | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	864		1,049
Consumer loans | 90 Days or More Past Due Loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Total	30		0
Consumer loans | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Total	448		407
Consumer loans | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Total	386		642
Consumer loans | Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	7,472		22,947
Year two, fiscal year before current fiscal year	22,481		29,445
Year three, two years before current fiscal year	27,294		38,774
Year four, three years before current fiscal year	38,220		10,302
Year five, four years before current fiscal year	9,828		3,340
More than five years before current fiscal year	54,408		50,613
Revolving Loans Amortized Cost Basis	431,436		438,817
Revolving Loans Converted to Term Loans	9,112		9,061
Total	600,251		603,299
Consumer loans | Performing | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	345,515		863,281
Year two, fiscal year before current fiscal year	787,382		343,203
Year three, two years before current fiscal year	308,544		363,901
Year four, three years before current fiscal year	321,091		211,294
Year five, four years before current fiscal year	178,895		59,288
More than five years before current fiscal year	99,088		59,512
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	2,040,515		1,900,479
Consumer loans | Performing | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	5,866		15,164
Year two, fiscal year before current fiscal year	13,311		25,884
Year three, two years before current fiscal year	30,004		15,787
Year four, three years before current fiscal year	14,866		1,588
Year five, four years before current fiscal year	1,700		337
More than five years before current fiscal year	58,528		53,917
Revolving Loans Amortized Cost Basis	976,315		956,339
Revolving Loans Converted to Term Loans	11,592		15,917
Total	1,112,182		1,084,933
Consumer loans | Non-performing loan held for sale | 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		48
Year three, two years before current fiscal year	3		51
Year four, three years before current fiscal year	173		1
Year five, four years before current fiscal year	105		0
More than five years before current fiscal year	1,029		855
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	600		179
Total	1,910		1,134
Consumer loans | Non-performing loan held for sale | 90 Days or More Past Due Loans | Automobile
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		71
Year two, fiscal year before current fiscal year	116		122
Year three, two years before current fiscal year	95		140
Year four, three years before current fiscal year	170		70
Year five, four years before current fiscal year	94		2
More than five years before current fiscal year	237		181
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	712		586
Consumer loans | Non-performing loan held for sale | 90 Days or More Past Due Loans | Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		0
Year two, fiscal year before current fiscal year	30		59
Year three, two years before current fiscal year	0		61
Year four, three years before current fiscal year	61		0
Year five, four years before current fiscal year	0		0
More than five years before current fiscal year	38		38
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	261		248
Total	390		406
Gross loan charge-offs
Gross loan charge-offs
Year one, gross loan charge-offs	0		1,014
Year two, gross loan charge-offs	522		1,883
Year three, gross loan charge-offs	297		1,511
Year four, gross loan charge-offs	348		1,015
Year five, gross loan charge-offs	152		519
More than five years gross loan charge-offs	762		2,245
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	59		131
Total	2,140		8,318
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	416,709		1,824,953
Year two, fiscal year before current fiscal year	1,720,855		854,030
Year three, two years before current fiscal year	802,792		772,815
Year four, three years before current fiscal year	723,701		492,961
Year five, four years before current fiscal year	421,284		250,075
More than five years before current fiscal year	711,377		524,794
Revolving Loans Amortized Cost Basis	5,321,319		5,155,993
Revolving Loans Converted to Term Loans	32,168		55,779
Total	10,150,205		9,931,400
Gross loan charge-offs
Total	28,456	14,293
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	402,895		1,769,585
Year two, fiscal year before current fiscal year	1,683,588		828,087
Year three, two years before current fiscal year	775,801		703,962
Year four, three years before current fiscal year	657,761		476,091
Year five, four years before current fiscal year	405,335		246,992
More than five years before current fiscal year	592,244		392,834
Revolving Loans Amortized Cost Basis	4,880,356		4,804,095
Revolving Loans Converted to Term Loans	8,136		6,006
Total	9,406,116		9,227,652
Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	13,814		30,755
Year two, fiscal year before current fiscal year	1,186		3,553
Year three, two years before current fiscal year	5,973		59,434
Year four, three years before current fiscal year	3,413		11,646
Year five, four years before current fiscal year	11,255		270
More than five years before current fiscal year	14,628		72,514
Revolving Loans Amortized Cost Basis	210,855		147,254
Revolving Loans Converted to Term Loans	3,766		10,762
Total	264,890		336,188
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		24,613
Year two, fiscal year before current fiscal year	36,081		13,479
Year three, two years before current fiscal year	13,898		9,415
Year four, three years before current fiscal year	62,525		4,296
Year five, four years before current fiscal year	4,373		2,813
More than five years before current fiscal year	52,761		7,382
Revolving Loans Amortized Cost Basis	217,195		201,053
Revolving Loans Converted to Term Loans	20,266		39,011
Total	407,099		302,062
Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		0
Year two, fiscal year before current fiscal year	0		8,911
Year three, two years before current fiscal year	7,120		4
Year four, three years before current fiscal year	2		928
Year five, four years before current fiscal year	321		0
More than five years before current fiscal year	51,744		52,064
Revolving Loans Amortized Cost Basis	12,913		3,591
Revolving Loans Converted to Term Loans	0		0
Total	72,100		65,498
Commercial and industrial | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		1,307
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	29,114,556		29,644,958
Gross loan charge-offs
Total	13,423	$ 8,798
Commercial Real Estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	638,695		2,338,118
Year two, fiscal year before current fiscal year	2,267,477		3,433,126
Year three, two years before current fiscal year	3,093,123		5,988,114
Year four, three years before current fiscal year	5,798,174		4,400,609
Year five, four years before current fiscal year	4,250,687		2,604,959
More than five years before current fiscal year	9,265,733		6,937,081
Revolving Loans Amortized Cost Basis	695,277		749,597
Revolving Loans Converted to Term Loans	78,455		78,621
Total	26,087,621		26,530,225
Commercial Real Estate | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	600,990		2,097,314
Year two, fiscal year before current fiscal year	2,070,782		2,941,270
Year three, two years before current fiscal year	2,622,556		5,310,807
Year four, three years before current fiscal year	5,052,632		3,883,333
Year five, four years before current fiscal year	3,667,440		2,302,480
More than five years before current fiscal year	8,058,437		6,086,608
Revolving Loans Amortized Cost Basis	514,996		597,266
Revolving Loans Converted to Term Loans	78,387		78,621
Total	22,666,220		23,297,699
Commercial Real Estate | Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		156,394
Year two, fiscal year before current fiscal year	127,965		380,852
Year three, two years before current fiscal year	308,325		289,669
Year four, three years before current fiscal year	293,431		192,614
Year five, four years before current fiscal year	218,617		55,739
More than five years before current fiscal year	359,533		327,732
Revolving Loans Amortized Cost Basis	165,641		141,164
Revolving Loans Converted to Term Loans	0		0
Total	1,473,512		1,544,164
Commercial Real Estate | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	37,705		84,410
Year two, fiscal year before current fiscal year	68,730		107,944
Year three, two years before current fiscal year	159,182		387,638
Year four, three years before current fiscal year	452,111		288,906
Year five, four years before current fiscal year	330,105		236,927
More than five years before current fiscal year	834,911		520,858
Revolving Loans Amortized Cost Basis	14,640		11,167
Revolving Loans Converted to Term Loans	68		0
Total	1,897,452		1,637,850
Commercial Real Estate | Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		0
Year two, fiscal year before current fiscal year	0		3,060
Year three, two years before current fiscal year	3,060		0
Year four, three years before current fiscal year	0		35,756
Year five, four years before current fiscal year	34,525		9,813
More than five years before current fiscal year	12,852		1,883
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	50,437		50,512
Commercial Real Estate | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	153,394		568,710
Year two, fiscal year before current fiscal year	563,135		680,260
Year three, two years before current fiscal year	619,201		346,587
Year four, three years before current fiscal year	333,597		102,776
Year five, four years before current fiscal year	83,090		25,228
More than five years before current fiscal year	72,943		47,665
Revolving Loans Amortized Cost Basis	1,143,795		1,284,863
Revolving Loans Converted to Term Loans	57,780		58,644
Total	3,026,935		3,114,733
Commercial Real Estate | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	153,394		545,597
Year two, fiscal year before current fiscal year	549,099		680,260
Year three, two years before current fiscal year	614,599		334,899
Year four, three years before current fiscal year	324,001		92,765
Year five, four years before current fiscal year	69,166		17,955
More than five years before current fiscal year	72,943		45,161
Revolving Loans Amortized Cost Basis	1,062,079		1,224,698
Revolving Loans Converted to Term Loans	24,850		58,644
Total	2,870,131		2,999,979
Commercial Real Estate | Construction | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		13,278
Year two, fiscal year before current fiscal year	13,263		0
Year three, two years before current fiscal year	4,527		664
Year four, three years before current fiscal year	646		5,069
Year five, four years before current fiscal year	9,447		0
More than five years before current fiscal year	0		2,504
Revolving Loans Amortized Cost Basis	29,494		16,691
Revolving Loans Converted to Term Loans	0		0
Total	57,377		38,206
Commercial Real Estate | Construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		9,835
Year two, fiscal year before current fiscal year	773		0
Year three, two years before current fiscal year	75		8,950
Year four, three years before current fiscal year	8,950		4,942
Year five, four years before current fiscal year	4,477		0
More than five years before current fiscal year	0		0
Revolving Loans Amortized Cost Basis	52,222		43,474
Revolving Loans Converted to Term Loans	32,930		0
Total	99,427		67,201
Commercial Real Estate | Construction | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year			0
Year two, fiscal year before current fiscal year			0
Year three, two years before current fiscal year			2,074
Year four, three years before current fiscal year			0
Year five, four years before current fiscal year			7,273
More than five years before current fiscal year			0
Revolving Loans Amortized Cost Basis			0
Revolving Loans Converted to Term Loans			0
Total			9,347
Commercial Real Estate | 90 Days or More Past Due Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial Real Estate | 90 Days or More Past Due Loans | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial Real Estate | 90 Days or More Past Due Loans | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0		0
Commercial and Industrial and Commercial Real Estate
Gross loan charge-offs
Year one, gross loan charge-offs	0		706
Year two, gross loan charge-offs	70		31,809
Year three, gross loan charge-offs	842		7,523
Year four, gross loan charge-offs	2,488		44,610
Year five, gross loan charge-offs	7,308		66,632
More than five years gross loan charge-offs	6,807		49,436
Revolving Loans Amortized Cost Basis	9,776		3,930
Revolving Loans Converted to Term Loans	14,588		2,148
Total	$ 41,879		$ 206,794