Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 460.6	$ 373.8
Provision for (Recovery of) Credit Losses	209.0	40.6
Charge-offs	209.1	27.5
Recoveries	(0.6)	(1.7)
Ending balance	461.1	388.6
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Balance, beginning of period	49.6	39.5
Provision for (recovery of) credit losses	3.7	(4.4)
Balance, end of period	53.3	35.1
Mortgage finance
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5.5	4.8
Provision for (Recovery of) Credit Losses	0.2	(0.3)
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	5.7	4.5
Municipal & nonprofit
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13.0	14.7
Provision for (Recovery of) Credit Losses	5.4	0.1
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	18.4	14.8
Tech & innovation
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	44.8	55.9
Provision for (Recovery of) Credit Losses	28.5	0.2
Charge-offs	20.8	12.1
Recoveries	(0.4)	(0.9)
Ending balance	52.9	44.9
Equity fund resources
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2.6	1.6
Provision for (Recovery of) Credit Losses	1.4	(0.2)
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	4.0	1.4
Other commercial and industrial
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	184.7	79.4
Provision for (Recovery of) Credit Losses	149.1	14.9
Charge-offs	160.0	0.9
Recoveries	(0.2)	(0.1)
Ending balance	174.0	93.5
CRE - owner occupied
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3.4	3.4
Provision for (Recovery of) Credit Losses	0.2	0.2
Charge-offs	0.0	0.0
Recoveries	0.0	(0.1)
Ending balance	3.6	3.7
Hotel franchise finance
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	37.7	35.3
Provision for (Recovery of) Credit Losses	2.8	(2.7)
Charge-offs	0.0	0.0
Recoveries	0.0	(0.6)
Ending balance	40.5	33.2
Other CRE - non-owner occupied
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	110.4	134.4
Provision for (Recovery of) Credit Losses	16.7	18.2
Charge-offs	27.7	14.5
Recoveries	0.0	0.0
Ending balance	99.4	138.1
Residential
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	23.7	19.7
Provision for (Recovery of) Credit Losses	0.0	0.0
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	23.7	19.7
Residential EBO
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0.0	0.0
Provision for (Recovery of) Credit Losses	0.0	0.0
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	0.0	0.0
Construction and land development
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	32.3	21.3
Provision for (Recovery of) Credit Losses	5.3	10.7
Charge-offs	0.0	0.0
Recoveries	0.0	0.0
Ending balance	37.6	32.0
Other
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2.5	3.3
Provision for (Recovery of) Credit Losses	(0.6)	(0.5)
Charge-offs	0.6	0.0
Recoveries	0.0	0.0
Ending balance	$ 1.3	$ 2.8

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- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

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- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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- Definition

Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-2

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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