Mortgage Loans - Loans in Mortgage Portfolio (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	$ 4,098,616		$ 4,098,616			$ 4,110,196
Cost basis and fair value adjustments, net	33,020		33,020			35,517
Allowance for loan losses for HFI loans	(8,246)	$ (7,656)	(8,246)	$ (7,656)	$ (8,247)	(7,707)	$ (8,026)	$ (8,730)
Total mortgage loans	4,123,390		4,123,390			4,138,006
Accrued interest receivable, net	11,901		11,901			11,364
Single-family
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	3,586,725		3,586,725			3,619,838
Purchase of HFI loans:	90,175	93,114	237,369	241,180
Amortized cost	823	820	1,527	1,272
Lower of cost or fair value adjustment at time of redesignation	(97)	(101)	(187)	(139)
Allowance reversed at time of redesignation	6	5	26	8
Amortized cost	0	77	0	77
Unpaid principal balance	309	14	969	2,345
Realized gains (losses), net	(7)	0	0	13
Multifamily
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	511,891		511,891			490,358
Purchase of HFI loans:	18,508	$ 13,153	46,658	$ 32,492
Mortgage loans
Loans in Mortgage Portfolio [Line Items]
Accrued interest receivable, net	$ 11,400		$ 11,400			$ 10,800