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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2025
Derivative |  |  |  |
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position | $ 269.7 | $ 255.7 |  |
Derivative, Notional Amount | 3,818.2 | 3,751.4 |  |
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months | $ 2.5 |  |  |
Maximum Length of Time Hedged in Cash Flow Hedge | 28 years |  |  |
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness | $ 37.3 | (22.0) | $ (21.1) |
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge | 0.0 | 0.0 | $ 0.0 |
Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 3,498.9 | 3,445.5 |  |
Not Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 319.3 | 305.9 |  |
Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 2,730.3 | 2,709.1 |  |
Interest Rate Swaps | Not Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 115.6 | 125.9 |  |
Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 127.3 | 139.1 |  |
Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 768.6 | 736.4 |  |
Forwards | Not Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 48.9 | 51.1 |  |
Total Return Swap | Not Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 154.8 | 128.9 |  |
Total Return Swap | Not Designated as Hedging Instrument | Credit Spreads and Interest Rate Volatility |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 0.0 | 0.0 |  | $ 700.0
Foreward Benchmark Interest Rate Lock | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 2,603.0 | 2,570.0 |  |
Receive Fixed/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 115.6 | 125.9 |  |
Receive Fixed/Pay Fixed | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 127.3 | 139.1 |  |
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument |  |  |  |
Derivative |  |  |  |
Derivative, Notional Amount | 768.6 | 736.4 |  |
Credit Exposure |  |  |  |
Derivative |  |  |  |
Credit Exposure on Derivatives | $ 0.0 | $ 0.5 |  |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 25 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480237/815-40-50-5 + Details
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- Definition The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 185 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480401/815-10-55-185 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4H -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4H + Details
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- Definition Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 21 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-21 + Details
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- Definition Amount of net gain (loss) recognized in earnings when a hedged firm commitment no longer qualifies as a fair value hedge. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 21 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476148/220-40-50-21 + Details
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- Definition Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480870/815-30-50-1 + Details
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