Derivative Financial Instruments - Clearinghouse Margin and Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative contracts
Initial margin cash collateral posted	$ 1.2	$ 0.6
Interest rate swaps
Derivative contracts
Cash pledged as collateral	1.2	0.6
Received cash as collateral	35.0	27.1
Securities received as collateral	53.3	40.9
Chicago Mercantile Exchange (CME) and London Clearing House (LCH)
Derivative contracts
Variation margin	$ 1.9	$ 0.7

Amount of cash collateral received.

No definition available.

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- Definition

Amount of variation margin cash paid under certain derivative contracts cleared through clearinghouses that is treated as a settlement and applied as a direct reduction of the fair value of the net derivative liability with such clearinghouses.

+ References

No definition available.

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- Definition

The amount of securities on deposit with clearing organizations and other entities which provide services necessary to operations of the Company. This item would include, for instance, securities advanced as refundable collateral for securities borrowed.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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- Definition

Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 13
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483444/210-20-55-13

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-Topic 210
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483466/210-20-50-3

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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/2003/role/disclosureRef
-Topic 815
-SubTopic 40
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-URI https://asc.fasb.org//1943274/2147480237/815-40-50-5

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- Definition

The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
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-Subparagraph (b)(1)
-SubTopic 30
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481420/860-30-50-1A

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