Loans and Allowance for Credit Losses for Loans - Internal Loan Classification Risk by Loan Portfolio Class 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
Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	403,888		1,579,982
Year two, fiscal year before current fiscal year	1,348,977		1,123,368
Year three, two years before current fiscal year	987,942		784,426
Year four, three years before current fiscal year	686,420		379,097
Year five, four years before current fiscal year	355,952		217,248
More than five years before current fiscal year	741,468		588,062
Revolving Loans Amortized Cost Basis	4,521,821		4,524,198
Revolving Loans Converted to Term Loans	57,725		34,162
Total	9,104,193		9,230,543
Gross loan charge-offs
Total	14,293	26,047
Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	402,170		1,494,417
Year two, fiscal year before current fiscal year	1,275,151		1,047,513
Year three, two years before current fiscal year	899,621		765,335
Year four, three years before current fiscal year	666,947		377,047
Year five, four years before current fiscal year	340,653		211,504
More than five years before current fiscal year	660,087		523,430
Revolving Loans Amortized Cost Basis	4,401,704		4,382,361
Revolving Loans Converted to Term Loans	35,540		29,798
Total	8,681,873		8,831,405
Commercial and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	1,718		70,807
Year two, fiscal year before current fiscal year	20,804		73,423
Year three, two years before current fiscal year	85,156		15,296
Year four, three years before current fiscal year	13,735		358
Year five, four years before current fiscal year	355		1,870
More than five years before current fiscal year	20,959		915
Revolving Loans Amortized Cost Basis	71,380		99,981
Revolving Loans Converted to Term Loans	139		139
Total	214,246		262,789
Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		3,100
Year two, fiscal year before current fiscal year	43,944		1,837
Year three, two years before current fiscal year	3,144		2,629
Year four, three years before current fiscal year	4,571		1,714
Year five, four years before current fiscal year	14,966		1,221
More than five years before current fiscal year	7,924		5,900
Revolving Loans Amortized Cost Basis	40,268		29,569
Revolving Loans Converted to Term Loans	22,046		4,225
Total	136,863		50,195
Commercial and industrial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		11,658
Year two, fiscal year before current fiscal year	9,078		595
Year three, two years before current fiscal year	21		1,166
Year four, three years before current fiscal year	1,167
Year four, three years before current fiscal year			(22)
Year five, four years before current fiscal year			2,653
Year five, four years before current fiscal year	(22)
More than five years before current fiscal year	52,498		57,817
Revolving Loans Amortized Cost Basis	8,469		12,287
Revolving Loans Converted to Term Loans	0		0
Total	71,211		86,154
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	31,705,464		31,970,047
Gross loan charge-offs
Total	8,798	$ 5,698
Commercial real estate | 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	18,181
Year four, three years before current fiscal year	0
Year five, four years before current fiscal year	10,000
More than five years before current fiscal year	11,910
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term Loans	0
Total	40,091
Commercial real estate | Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	409,561		4,272,246
Year two, fiscal year before current fiscal year	4,155,387		6,738,948
Year three, two years before current fiscal year	6,639,835		5,052,212
Year four, three years before current fiscal year	5,011,154		3,022,501
Year five, four years before current fiscal year	2,957,297		2,469,773
More than five years before current fiscal year	8,055,377		5,957,963
Revolving Loans Amortized Cost Basis	785,570		622,497
Revolving Loans Converted to Term Loans	134,772		107,099
Total	28,148,953		28,243,239
Commercial real estate | Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	384,214		4,088,835
Year two, fiscal year before current fiscal year	3,928,977		6,630,322
Year three, two years before current fiscal year	6,314,486		4,791,190
Year four, three years before current fiscal year	4,607,445		2,789,275
Year five, four years before current fiscal year	2,674,613		2,329,385
More than five years before current fiscal year	7,345,774		5,385,809
Revolving Loans Amortized Cost Basis	779,366		618,056
Revolving Loans Converted to Term Loans	134,472		104,839
Total	26,169,347		26,737,711
Commercial real estate | Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	6,379		125,296
Year two, fiscal year before current fiscal year	106,984		82,917
Year three, two years before current fiscal year	197,652		248,900
Year four, three years before current fiscal year	231,119		184,720
Year five, four years before current fiscal year	160,474		69,949
More than five years before current fiscal year	362,966		358,059
Revolving Loans Amortized Cost Basis	3,007		26
Revolving Loans Converted to Term Loans	83		183
Total	1,068,664		1,070,050
Commercial real estate | Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	18,968		58,115
Year two, fiscal year before current fiscal year	119,426		25,709
Year three, two years before current fiscal year	127,697		12,122
Year four, three years before current fiscal year	172,590		48,506
Year five, four years before current fiscal year	122,210		70,439
More than five years before current fiscal year	346,637		214,095
Revolving Loans Amortized Cost Basis	3,197		4,415
Revolving Loans Converted to Term Loans	217		2,077
Total	910,942		435,478
Commercial real estate | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	137,671		760,480
Year two, fiscal year before current fiscal year	832,805		675,097
Year three, two years before current fiscal year	605,504		276,612
Year four, three years before current fiscal year	212,244		10,318
Year five, four years before current fiscal year	22,723		40,584
More than five years before current fiscal year	68,121		61,228
Revolving Loans Amortized Cost Basis	1,586,612		1,762,890
Revolving Loans Converted to Term Loans	90,831		139,599
Total	3,556,511		3,726,808
Commercial real estate | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	137,671		753,759
Year two, fiscal year before current fiscal year	826,057		655,198
Year three, two years before current fiscal year	587,323		267,336
Year four, three years before current fiscal year	201,115		10,318
Year five, four years before current fiscal year	12,723		40,584
More than five years before current fiscal year	56,211		43,560
Revolving Loans Amortized Cost Basis	1,550,191		1,762,890
Revolving Loans Converted to Term Loans	90,831		139,599
Total	3,462,122		3,673,244
Commercial real estate | Construction | Special Mention
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	0
Year four, three years before current fiscal year	2,136
Year five, four years before current fiscal year	0
More than five years before current fiscal year	0
Revolving Loans Amortized Cost Basis	36,421
Revolving Loans Converted to Term Loans	0
Total	38,557
Commercial real estate | Construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, current fiscal year	0		6,721
Year two, fiscal year before current fiscal year	6,748		0
Year three, two years before current fiscal year	0		9,276
Year four, three years before current fiscal year	8,993		0
Year five, four years before current fiscal year	0		0
More than five years before current fiscal year	0		17,668
Revolving Loans Amortized Cost Basis	0		0
Revolving Loans Converted to Term Loans	0		0
Total	15,741		33,665
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			19,899
Year three, two years before current fiscal year			0
Year four, three years before current fiscal year			0
Year five, four years before current fiscal year			0
More than five years before current fiscal year			0
Revolving Loans Amortized Cost Basis			0
Revolving Loans Converted to Term Loans			0
Total			19,899
Commercial and Industrial and Commercial Real Estate
Gross loan charge-offs
Year one, gross loan charge-offs	0		307
Year two, gross loan charge-offs	1,846		12,919
Year three, gross loan charge-offs	2,211		28,438
Year four, gross loan charge-offs	271		6,946
Year five, gross loan charge-offs	704		5,031
More than five years gross loan charge-offs	14,305		13,446
Revolving Loans Amortized Cost Basis	3,600		3,729
Revolving Loans Converted to Term Loans	154		145
Total	$ 23,091		$ 70,961