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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Derivative |  |  |  |  |
Aggregate fair value of all derivative instruments with credit risk-related contingent features in a liability position | $ 76.4 |  | $ 76.4 |  | $ 74.0
Approximate amount of net deferred gains on derivative instruments expected to be amortized during the next twelve months |  |  | 26.2 |  |
Component of Derivative Gain (Loss) Excluded from the Assessment of Hedge Effectiveness | (9.7) | $ 10.3 | (7.2) | $ 13.7 |
Discontinued Hedge Accounting Due to Instrument No Longer Qualifying as Fair Value Hedge | 0.0 | $ 0.0 | 0.0 | $ 0.0 |
Derivative, Notional Amount | 2,266.4 |  | 2,266.4 |  | 1,753.9
Derivative Asset, Fair Value, Gross Asset | 80.6 |  | $ 80.6 |  | 89.1
Maximum Length of Time Hedged in Cash Flow Hedge |  |  | 30 years 6 months |  |
Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 1,991.6 |  | $ 1,991.6 |  | 1,490.7
Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 274.8 |  | 274.8 |  | 263.2
Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 1,401.6 |  | 1,401.6 |  | 932.9
Interest Rate Swaps | Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 132.0 |  | 132.0 |  | 132.0
Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 159.6 |  | 159.6 |  | 168.9
Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 590.0 |  | 590.0 |  | 557.8
Forwards | Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 54.0 |  | 54.0 |  | 54.3
Forwards | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 1,242.0 |  | 1,242.0 |  | 764.0
Total Return Swap | Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 88.8 |  | 88.8 |  | 76.9
Embedded Derivative in Modified Coinsurance Arrangement | Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 0.0 |  | 0.0 |  | 0.0
Receive Fixed/Pay Fixed | Interest Rate Swaps | Not Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 132.0 |  | 132.0 |  | 132.0
Receive Fixed/Pay Fixed | Interest Rate Swaps | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 159.6 |  | 159.6 |  | 168.9
Receive Fixed/Pay Fixed | Interest Rate Swaps | Fair Value Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative |  |  |  |  |
Derivative, Notional Amount | 590.0 |  | 590.0 |  | 557.8
Credit Exposure |  |  |  |  |
Derivative |  |  |  |  |
Credit Exposure on Derivatives | $ 0.0 |  | $ 0.0 |  | $ 1.7

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- Definition Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 22 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483444/210-20-55-22 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483466/210-20-50-3 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483444/210-20-55-7 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4B Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 4D -Subparagraph (c)(2) -SubTopic 20 -Topic 860 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481326/860-20-50-4D + 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 4C -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480434/815-10-50-4C Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 815 -SubTopic 25 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480238/815-25-50-1 + Details
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