Segment Reporting (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2025 USD ($) branch	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	$ 285,941	$ 257,858
Noninterest Income	58,776	64,985
Provision for Loan, Lease, and Other Losses	13,003	24,001
Noninterest Expense	210,619	197,657
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	121,095	101,185
Income Tax Expense (Benefit)	19,409	20,016
Net Income (Loss) Attributable to Parent, Total	101,687	81,169
Goodwill	$ 1,104,992		$ 1,104,992
Number of Reportable Segments | branch	3
Interest Income (Expense), after Provision for Loan Loss	$ 272,938	233,857
Labor and Related Expense	123,897	119,395
Information Technology and Data Processing	27,139	26,200
Occupancy, Net	15,381	13,633
Marketing and Advertising Expense	6,386	6,517
Equipment Expense	4,527	4,599
Professional Fees	6,083	4,672
Federal Deposit Insurance Corporation Premium Expense	10,436	13,946
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	11,974	4,513
Commercial and business lending	30,294,127		29,768,586
Assets	43,309,136		$ 43,023,068
Gain (Loss) on Sale of Mortgage Loans	(6,976)	0
Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Technology expense	61	61
Community, Consumer and Business [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Occupancy expense	3,000	2,000
Risk Management and Shared Services [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Equipment expense	11,000	10,000
Operating Segments
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	285,941	257,858
Net intersegment interest income (expense)	0	0
Segment net interest income	285,941	257,858
Noninterest Income	58,776	64,985
Provision for Loan, Lease, and Other Losses	13,003	24,001
Noninterest Expense	210,619	197,657
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	121,095	101,185
Income Tax Expense (Benefit)	19,409	20,016
Net Income (Loss) Attributable to Parent, Total	101,687	81,169
Goodwill	1,104,992	1,104,992
Interest Income (Expense), before Provision	344,717	322,843
Interest Income (Expense), after Provision for Loan Loss	331,714	298,842
Labor and Related Expense	123,897	119,395
Information Technology and Data Processing	27,139	26,200
Occupancy, Net	15,381	13,633
Marketing and Advertising Expense	6,386	6,517
Equipment Expense	4,527	4,599
Professional Fees	6,083	4,672
Payments of Financing Costs	2,594	1,979
Federal Deposit Insurance Corporation Premium Expense	10,436	13,946
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	11,974	4,513
Allocated indirect expense	0	0
Commercial and business lending	30,294,127	29,494,263
Assets	43,309,136	41,137,084
Operating Segments | Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	227,286	239,729
Net intersegment interest income (expense)	(93,342)	(107,565)
Segment net interest income	133,944	132,164
Noninterest Income	12,903	11,869
Provision for Loan, Lease, and Other Losses	19,014	14,998
Noninterest Expense	45,152	42,778
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	82,681	86,257
Income Tax Expense (Benefit)	15,696	17,808
Net Income (Loss) Attributable to Parent, Total	66,985	68,449
Goodwill	525,836	525,836
Interest Income (Expense), before Provision	146,847	144,033
Interest Income (Expense), after Provision for Loan Loss	127,833	129,035
Labor and Related Expense	21,327	20,430
Information Technology and Data Processing	591	601
Occupancy, Net	0	0
Marketing and Advertising Expense	934	937
Equipment Expense	0	1
Professional Fees	201	135
Payments of Financing Costs	810	246
Federal Deposit Insurance Corporation Premium Expense	0	0
Amortization of Intangible Assets	0	0
Other Noninterest Expense	781	763
Allocated indirect expense	20,508	19,665
Commercial and business lending	17,400,092	16,171,212
Assets	18,202,227	16,973,027
Operating Segments | Community, Consumer and Business [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	62,496	61,395
Net intersegment interest income (expense)	135,656	143,987
Segment net interest income	198,152	205,382
Noninterest Income	49,100	47,048
Provision for Loan, Lease, and Other Losses	6,072	7,256
Noninterest Expense	136,817	134,062
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	104,363	111,112
Income Tax Expense (Benefit)	21,916	23,335
Net Income (Loss) Attributable to Parent, Total	82,447	87,777
Goodwill	579,156	579,156
Interest Income (Expense), before Provision	247,252	252,430
Interest Income (Expense), after Provision for Loan Loss	241,180	245,174
Labor and Related Expense	59,871	60,569
Information Technology and Data Processing	13,045	11,349
Occupancy, Net	27	22
Marketing and Advertising Expense	837	859
Equipment Expense	1,103	1,398
Professional Fees	809	401
Payments of Financing Costs	1,344	1,652
Federal Deposit Insurance Corporation Premium Expense	0	0
Amortization of Intangible Assets	0	0
Other Noninterest Expense	7,490	6,388
Allocated indirect expense	52,291	51,424
Commercial and business lending	12,417,213	12,770,285
Assets	13,245,770	13,600,201
Operating Segments | Risk Management and Shared Services [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	(3,841)	(43,266)
Net intersegment interest income (expense)	(42,314)	(36,422)
Segment net interest income	(46,155)	(79,688)
Noninterest Income	(3,227)	6,068
Provision for Loan, Lease, and Other Losses	(12,083)	1,747
Noninterest Expense	28,651	20,817
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	(65,950)	(96,184)
Income Tax Expense (Benefit)	(18,203)	(21,127)
Net Income (Loss) Attributable to Parent, Total	(47,747)	(75,058)
Goodwill	0	0
Interest Income (Expense), before Provision	(49,382)	(73,620)
Interest Income (Expense), after Provision for Loan Loss	(37,299)	(75,367)
Labor and Related Expense	42,699	38,396
Information Technology and Data Processing	13,503	14,250
Occupancy, Net	15,354	13,611
Marketing and Advertising Expense	4,615	4,721
Equipment Expense	3,424	3,200
Professional Fees	5,073	4,136
Payments of Financing Costs	440	81
Federal Deposit Insurance Corporation Premium Expense	10,436	13,946
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	3,703	(2,638)
Allocated indirect expense	(72,799)	(71,089)
Commercial and business lending	476,822	552,766
Assets	$ 11,861,139	$ 10,563,856