Value of input used to measure debt instrument, including, but not limited to, convertible and non-convertible debt.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount, after tax, before reclassification adjustment, of unrealized gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Fair Value Accounting - Change in Level 3 Liabilities Measured at Fair Value on Recurring Basis (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes included in OCI, net of tax	$ (4.1)	$ (0.5)	$ (3.0)	$ (1.0)
Junior subordinated debt	69.0		69.0		$ 65.0
Fair Value, Recurring \| Significant Unobservable Inputs (Level 3)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Junior subordinated debt	69.0		69.0		$ 65.0
Junior Subordinated Debt
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in fair value	$ (5.4)	(0.7)	$ (3.9)	(1.4)
Debt Instrument, measurement input	0.0630		0.0630		0.0743
Junior Subordinated Debt \| Significant Unobservable Inputs (Level 3)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Junior subordinated debt	$ 69.0		$ 69.0		$ 65.0
Junior Subordinated Debt \| Fair Value, Recurring
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(63.2)	(63.5)	(64.7)	(62.8)
Ending balance	$ (68.6)	$ (64.2)	$ (68.6)	$ (64.2)