Loans, Leases and Allowance for Credit Losses - Allowances for Credit Losses (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 388.6	$ 340.3	$ 373.8	$ 336.7
Provision for (Recovery of) Credit Losses	35.7	34.3	76.3	47.7
Charge-offs	35.3	22.9	62.8	33.1
Recoveries	(5.7)	(0.1)	(7.4)	(0.5)
Ending balance	394.7	351.8	394.7	351.8
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Balance, beginning of period	35.1	33.1	39.5	31.6
(Recovery of) provision for credit losses	4.1	2.8	(0.3)	4.3
Balance, end of period	39.2	35.9	39.2	35.9
Warehouse lending
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6.3	7.3	6.4	5.8
Provision for (Recovery of) Credit Losses	(0.4)	(0.8)	(0.5)	0.7
Charge-offs	0.0	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	5.9	6.5	5.9	6.5
Municipal & nonprofit
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	14.8	13.9	14.7	14.7
Provision for (Recovery of) Credit Losses	(3.5)	0.1	(3.4)	(0.7)
Charge-offs	0.0	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	11.3	14.0	11.3	14.0
Tech & innovation
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	44.9	48.0	55.9	42.1
Provision for (Recovery of) Credit Losses	10.4	(1.5)	10.6	4.4
Charge-offs	9.7	1.5	21.8	1.5
Recoveries	(0.1)	0.0	(1.0)	0.0
Ending balance	45.7	45.0	45.7	45.0
Equity fund resources
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1.4	1.2	1.6	1.3
Provision for (Recovery of) Credit Losses	0.8	0.5	0.6	0.4
Charge-offs	0.0	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	2.2	1.7	2.2	1.7
Other commercial and industrial
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	91.7	67.1	77.8	81.4
Provision for (Recovery of) Credit Losses	23.7	20.8	38.4	8.4
Charge-offs	6.7	3.7	7.6	6.0
Recoveries	(0.5)	(0.1)	(0.6)	(0.5)
Ending balance	109.2	84.3	109.2	84.3
CRE - owner occupied
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3.7	6.2	3.4	6.0
Provision for (Recovery of) Credit Losses	0.7	(1.2)	0.9	(1.0)
Charge-offs	0.5	0.0	0.5	0.0
Recoveries	0.0	0.0	(0.1)	0.0
Ending balance	3.9	5.0	3.9	5.0
Hotel franchise finance
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	33.2	35.8	35.3	33.4
Provision for (Recovery of) Credit Losses	2.8	3.8	0.1	9.1
Charge-offs	0.0	0.0	0.0	2.9
Recoveries	0.0	0.0	(0.6)	0.0
Ending balance	36.0	39.6	36.0	39.6
Other CRE - non-owner occupied
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	138.1	104.7	134.4	96.0
Provision for (Recovery of) Credit Losses	(0.7)	17.4	17.5	31.1
Charge-offs	17.5	17.6	32.0	22.6
Recoveries	(5.1)	0.0	(5.1)	0.0
Ending balance	125.0	104.5	125.0	104.5
Residential
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	19.7	22.1	19.7	23.1
Provision for (Recovery of) Credit Losses	0.2	(3.3)	0.2	(4.3)
Charge-offs	0.0	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	19.9	18.8	19.9	18.8
Residential EBO
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0.0	0.0	0.0	0.0
Provision for (Recovery of) Credit Losses	0.0	0.0	0.0	0.0
Charge-offs	0.0	0.0	0.0	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	0.0	0.0	0.0	0.0
Construction and land development
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	32.0	31.9	21.3	30.4
Provision for (Recovery of) Credit Losses	1.9	(2.0)	12.6	(0.5)
Charge-offs	0.3	0.0	0.3	0.0
Recoveries	0.0	0.0	0.0	0.0
Ending balance	33.6	29.9	33.6	29.9
Other
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2.8	2.1	3.3	2.5
Provision for (Recovery of) Credit Losses	(0.2)	0.5	(0.7)	0.1
Charge-offs	0.6	0.1	0.6	0.1
Recoveries	0.0	0.0	0.0	0.0
Ending balance	$ 2.0	$ 2.5	$ 2.0	$ 2.5

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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
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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
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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
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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
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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
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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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