Mortgage Servicing Assets - Assumptions and Sensitivity of MSR’s (Details) - Commercial Mortgage Backed Securities - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Minimum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Escrow earn rate	3.92%	3.94%
Residual cash flows discount rate	6.97%	6.96%
Expected defaults	1.00%	1.00%
Loan assumption rate	8.00%	8.00%
Maximum
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Escrow earn rate	4.11%	4.09%
Residual cash flows discount rate	10.83%	10.84%
Expected defaults	1.50%	2.00%
Loan assumption rate	45.00%	45.00%
Weighted Average
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Escrow earn rate	4.10%	4.08%
Effect on fair value from 10% adverse change	$ (29)	$ (29)
Effect on fair value from 20% adverse change	$ (57)	$ (57)
Residual cash flows discount rate	10.58%	10.58%
Effect on Fair Value of a 10% adverse change	$ (19)	$ (19)
Effect on Fair Value of a 20% adverse change	$ (36)	$ (36)
Expected defaults	1.03%	1.01%
Effect on fair value from 10% adverse change	$ (2)	$ (2)
Effect on fair value from 20% adverse change	$ (3)	$ (3)
Loan assumption rate	9.83%	10.05%
Effect on fair value from 10% adverse change	$ (6)	$ (6)
Effect on fair value from 20% adverse change	$ (12)	$ (13)

Interest rate used to account for mortgage loan at fair value upon assumption.

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Adverse Change in Default Rate

+ References

No definition available.

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Adverse Change in Escrow Earn Rate

+ References

No definition available.

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 10 Percent Adverse Change in Loan Assumptions Rate

+ References

No definition available.

+ Details

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Adverse Change in Default Rate

+ References

No definition available.

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Adverse Change in Escrow Earn Rate

+ References

No definition available.

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- Definition

Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 20 Percent Adverse Change in Loan Assumption Rate

+ References

No definition available.

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- Definition

Servicing Assets And Servicing Liabilities At Fair Value, Assumptions Used To Estimate Fair Value, Escrow Earn Rate

+ References

No definition available.

+ Details

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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

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- Definition

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

+ References

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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 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-4

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- Definition

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-2

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- Definition

Percentage of contractually collectible principal associated with a financial asset expected not to be collected due to default by the borrower.

+ References

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