Mortgage Loans Held for Portfolio (Mortgage Loans Held for Portfolio by Collateral or Guarantee Type) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 14,823	$ 14,453
US Government Agency Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	351	356
Conventional Mortgage Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, before Fees, Gross	$ 14,472	$ 14,097

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

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