Mortgage Loans - Loans in Mortgage Portfolio (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	$ 4,095,019		$ 4,095,019			$ 4,110,196
Cost basis and fair value adjustments, net	33,359		33,359			35,517
Allowance for loan losses for HFI loans	(8,247)	$ (8,026)	(8,247)	$ (8,026)	$ (7,532)	(7,707)	$ (8,379)	$ (8,730)
Total mortgage loans	4,120,131		4,120,131			4,138,006
Accrued interest receivable, net	11,678		11,678			11,364
Single-family
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	3,593,460		3,593,460			3,619,838
Purchase of HFI loans:	83,567	85,776	147,194	148,066
Amortized cost	194	216	704	452
Lower of cost or fair value adjustment at time of redesignation	(21)	(18)	(90)	(38)
Allowance reversed at time of redesignation	3	4	20	3
Unpaid principal balance	660	1,832	660	2,331
Realized gains (losses), net	7	8	7	13
Multifamily
Loans in Mortgage Portfolio [Line Items]
Total unpaid principal balance of mortgage loans	501,559		501,559			490,358
Purchase of HFI loans:	16,636	$ 9,271	28,150	$ 19,339
Mortgage loans
Loans in Mortgage Portfolio [Line Items]
Accrued interest receivable, net	$ 11,200		$ 11,200			$ 10,800