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Summary of Significant Accounting Policies (Narrative) (Details)	9 Months Ended
	Sep. 30, 2025 USD ($) segment	Dec. 31, 2024 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | segment	1
Monthly Fee to Participate in our Portfolio Program	$ 599
Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	15,600,000	$ 342,700,000
Restricted Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	$ 478,600,000	$ 497,000,000.0

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Monthly Fee to Participate in our Portfolio Program

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The amount of cash as of the balance sheet date that is not insured by the Federal Deposit Insurance Corporation.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

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-Section 55
-Paragraph 54
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-Publisher FASB
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-Topic 280
-SubTopic 10
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-Section 50
-Paragraph 18
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