Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	$ 307,190	$ 285,941
Noninterest Income	75,857	58,776
Provision for Loan, Lease, and Other Losses	11,001	13,003
Noninterest Expense	219,163	210,619
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	152,883	121,095
Income Tax Expense (Benefit)	33,248	19,409
Net Income (Loss) Attributable to Parent, Total	119,635	101,687
Goodwill	1,104,992		$ 1,104,992
Interest Income (Expense), after Provision for Loan Loss	296,189	272,938
Labor and Related Expense	135,172	123,897
Information Technology and Data Processing	29,736	27,139
Occupancy, Net	13,725	15,381
Marketing and Advertising Expense	7,827	6,386
Equipment Expense	5,610	4,527
Professional Fees	6,721	6,083
Federal Deposit Insurance Corporation Premium Expense	8,837	10,436
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	7,625	11,974
Commercial and business lending	31,798,164		31,163,614
Assets	45,593,740		$ 45,202,596
Gain (Loss) on Sale of Mortgage Loans	0	(6,976)
Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Technology expense	100	100
Community, Consumer and Business [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Occupancy expense	6,200	5,900
Risk Management and Shared Services [Member]
Segment Income Statement Data Abstract
A portion of total depreciation Equipment expense	5,900	7,900
Operating Segments
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	307,190	285,941
Net intersegment interest income (expense)	0	0
Segment net interest income	307,190	285,941
Noninterest Income	75,857	58,776
Provision for Loan, Lease, and Other Losses	11,001	13,003
Noninterest Expense	219,163	210,619
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	152,883	121,095
Income Tax Expense (Benefit)	33,248	19,409
Net Income (Loss) Attributable to Parent, Total	119,635	101,687
Goodwill	1,104,992	1,104,992
Interest Income (Expense), before Provision	383,047	344,717
Interest Income (Expense), after Provision for Loan Loss	372,046	331,714
Labor and Related Expense	135,172	123,897
Information Technology and Data Processing	29,736	27,139
Occupancy, Net	13,725	15,381
Marketing and Advertising Expense	7,827	6,386
Equipment Expense	5,610	4,527
Professional Fees	6,721	6,083
Payments of Financing Costs	1,707	2,594
Federal Deposit Insurance Corporation Premium Expense	8,837	10,436
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	7,625	11,974
Allocated indirect expense	0	0
Commercial and business lending	31,798,164	30,294,127
Assets	45,593,740	43,309,136
Operating Segments | Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	231,105	227,286
Net intersegment interest income (expense)	(102,712)	(96,221)
Segment net interest income	128,393	131,065
Noninterest Income	13,891	12,903
Provision for Loan, Lease, and Other Losses	20,660	19,014
Noninterest Expense	49,730	56,135
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	71,894	68,819
Income Tax Expense (Benefit)	13,259	12,786
Net Income (Loss) Attributable to Parent, Total	58,635	56,033
Goodwill	525,836	525,836
Interest Income (Expense), before Provision	142,284	143,968
Interest Income (Expense), after Provision for Loan Loss	121,624	124,954
Labor and Related Expense	23,550	21,327
Information Technology and Data Processing	823	591
Occupancy, Net	217	146
Marketing and Advertising Expense	969	934
Equipment Expense	6	6
Professional Fees	256	201
Payments of Financing Costs	488	811
Federal Deposit Insurance Corporation Premium Expense	0	0
Amortization of Intangible Assets	0	0
Other Noninterest Expense	722	781
Allocated indirect expense	22,699	31,339
Commercial and business lending	18,806,881	17,400,092
Assets	19,571,725	17,678,473
Operating Segments | Community, Consumer and Business [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	68,436	62,496
Net intersegment interest income (expense)	130,030	145,379
Segment net interest income	198,466	207,875
Noninterest Income	55,943	49,078
Provision for Loan, Lease, and Other Losses	6,934	6,072
Noninterest Expense	156,082	154,484
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	91,393	96,397
Income Tax Expense (Benefit)	19,192	20,244
Net Income (Loss) Attributable to Parent, Total	72,201	76,153
Goodwill	579,156	579,156
Interest Income (Expense), before Provision	254,409	256,953
Interest Income (Expense), after Provision for Loan Loss	247,475	250,881
Labor and Related Expense	64,953	59,872
Information Technology and Data Processing	14,124	13,045
Occupancy, Net	8,351	8,434
Marketing and Advertising Expense	688	837
Equipment Expense	2,075	2,030
Professional Fees	682	814
Payments of Financing Costs	940	1,344
Federal Deposit Insurance Corporation Premium Expense	0	0
Amortization of Intangible Assets	0	0
Other Noninterest Expense	7,681	7,402
Allocated indirect expense	56,588	60,706
Commercial and business lending	12,609,186	12,417,213
Assets	13,687,627	12,886,713
Operating Segments | Risk Management and Shared Services [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	7,649	(3,841)
Net intersegment interest income (expense)	(27,318)	(49,158)
Segment net interest income	(19,669)	(52,999)
Noninterest Income	6,023	(3,205)
Provision for Loan, Lease, and Other Losses	(16,593)	(12,083)
Noninterest Expense	13,351	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	(10,404)	(44,121)
Income Tax Expense (Benefit)	797	(13,621)
Net Income (Loss) Attributable to Parent, Total	(11,201)	(30,500)
Goodwill	0	0
Interest Income (Expense), before Provision	(13,646)	(56,204)
Interest Income (Expense), after Provision for Loan Loss	2,947	(44,121)
Labor and Related Expense	46,669	42,698
Information Technology and Data Processing	14,789	13,503
Occupancy, Net	5,157	6,801
Marketing and Advertising Expense	6,170	4,615
Equipment Expense	3,529	2,491
Professional Fees	5,783	5,068
Payments of Financing Costs	279	439
Federal Deposit Insurance Corporation Premium Expense	8,837	10,436
Amortization of Intangible Assets	2,203	2,203
Other Noninterest Expense	(778)	3,791
Allocated indirect expense	(79,287)	(92,045)
Commercial and business lending	382,097	476,822
Assets	$ 12,334,388	$ 12,743,950