Mortgage Loans - Loans Purchased and Sold (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Single-family \| Held for Investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Purchases	$ 99,428	$ 98,243	$ 270,677	$ 245,751
Single-family \| Held-for-Sale
Financing Receivable, Allowance for Credit Loss [Line Items]
Sales	707	658	1,962	1,657
Multifamily \| Held for Investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Purchases	24,522	7,867	37,099	14,283
Multifamily \| Held-for-Sale
Financing Receivable, Allowance for Credit Loss [Line Items]
Purchases	195	6,028	7,722	19,068
Sales	$ 1,781	$ 6,606	$ 16,632	$ 19,671

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.

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