Mortgage Loans Held for Portfolio (Narrative) (Details) - Residential Portfolio Segment - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Accrued Interest, after Allowance for Credit Loss	$ 108	$ 107
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	$ 6	$ 6
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Accrued interest receivable	Accrued interest receivable
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Percent Past Due	0.00%	0.00%

Amount, after allowance for credit loss, of accrued interest on financing receivable.

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-Topic 326
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Indicates line item in statement of financial position that includes accrued interest, after allowance for credit loss, on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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
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Percentage of financing receivable balance that is past due.

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