Mortgage Loans - Nonaccrual Loans (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 31,734	$ 30,393	$ 30,760	$ 29,101
Total interest income recognized	46	52
Single-family
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	116	103
Recorded investment in nonaccrual loans	28,359	27,691	27,448	26,584
Total interest income recognized	44	48
Single-family \| 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	27,148	26,335	26,221	25,218
Total interest income recognized	42	46
Single-family \| 15-year or less, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	681	771	692	770
Total interest income recognized	1	1
Single-family \| Adjustable-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	118	122	114	114
Total interest income recognized	0	0
Single-family \| Other
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	412	463	421	482
Total interest income recognized	1	1
Multifamily
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	8	10
Recorded investment in nonaccrual loans	3,375	2,702	$ 3,312	$ 2,517
Total interest income recognized	$ 2	$ 4

Amount of writeoff of accrued interest on financing receivable recognized by reversing interest income.

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