Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	$ 262,509			$ 254,244			$ 776,960	$ 786,171
Net intersegment interest income (expense)	0			0			0	0
Segment net interest income	262,509			254,244			776,960	786,171
Noninterest Income	67,221			66,579			197,365	194,195
Revenues, Total	329,730			320,823			974,325	980,366
Provision for Loan, Lease, and Other Losses	20,991			21,943			68,000	62,014
Noninterest Expense	200,597			196,205			594,115	574,291
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	108,142			102,674			312,211	344,061
Income Tax Expense (Benefit)	20,124			19,426			27,451	70,299
Net Income (Loss) Attributable to Parent, Total	88,018	$ 115,573	$ 81,169	83,248	$ 87,154	$ 103,360	284,760	273,762
Goodwill	1,104,992			1,104,992			1,104,992	1,104,992	$ 1,104,992
Operating Segments | Corporate and Commercial Specialty [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	254,935			250,365			749,062	710,031
Net intersegment interest income (expense)	(98,898)			(106,675)			(291,872)	(288,366)
Segment net interest income	156,037			143,690			457,190	421,665
Noninterest Income	37,017			34,086			106,570	99,254
Revenues, Total	193,054			177,776			563,761	520,919
Provision for Loan, Lease, and Other Losses	17,009			14,066			48,930	41,523
Noninterest Expense	65,415			63,265			197,159	186,521
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	110,630			100,445			317,672	292,876
Income Tax Expense (Benefit)	20,999			19,293			59,845	54,104
Net Income (Loss) Attributable to Parent, Total	89,630			81,152			257,827	238,772
Goodwill	525,836			525,836			525,836	525,836
Operating Segments | Community, Consumer, and Business [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	56,574			67,139			172,575	219,883
Net intersegment interest income (expense)	135,862			123,900			401,353	317,820
Segment net interest income	192,436			191,039			573,928	537,703
Noninterest Income	26,009			29,670			75,921	85,870
Revenues, Total	218,445			220,709			649,848	623,573
Provision for Loan, Lease, and Other Losses	5,195			7,381			17,611	21,467
Noninterest Expense	115,656			108,127			333,711	328,790
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	97,594			105,202			298,526	273,316
Income Tax Expense (Benefit)	20,495			22,092			62,691	57,396
Net Income (Loss) Attributable to Parent, Total	77,099			83,109			235,835	215,920
Goodwill	579,156			579,156			579,156	579,156
Operating Segments | Risk Management and Shared Serivies [Member]
Segment Income Statement Data Abstract
Interest Income (Expense), Operating	(49,001)			(63,260)			(144,677)	(143,743)
Net intersegment interest income (expense)	(36,964)			(17,225)			(109,481)	(29,454)
Segment net interest income	(85,964)			(80,485)			(254,158)	(173,197)
Noninterest Income	4,196			2,823			14,874	9,071
Revenues, Total	(81,768)			(77,663)			(239,284)	(164,126)
Provision for Loan, Lease, and Other Losses	(1,213)			496			1,459	(975)
Noninterest Expense	19,526			24,814			63,245	58,980
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest, Total	(100,081)			(102,972)			(303,988)	(222,131)
Income Tax Expense (Benefit)	(21,370)			(21,959)			(95,085)	(41,202)
Net Income (Loss) Attributable to Parent, Total	(78,711)			(81,013)			(208,902)	(180,929)
Goodwill	$ 0			$ 0			$ 0	$ 0