Debt - Total Debt (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Net [Abstract]
Total Debt	$ 2,423,316		$ 2,423,316		$ 2,169,685
Interest Expense [Abstract]
Interest Expense, Total	11,392	$ 15,130	39,039	$ 46,498
Held by consolidated trusts
Debt Net [Abstract]
Total Debt	2,138,420		2,138,420		1,898,355
Interest Expense [Abstract]
Interest Expense, Total	10,847	13,324	36,269	41,001
Held by Freddie Mac
Debt Net [Abstract]
Short-term Debt Balance Net	17,648		17,648		101,034
Long-term Debt Balance, Net	267,248		267,248		170,296
Total Debt	284,896		284,896		$ 271,330
Interest Expense [Abstract]
Interest Expense, Short-term Borrowings	38	499	598	1,419
Interest Expense, Long-term Debt	507	1,307	2,172	4,078
Interest Expense, Total	$ 545	$ 1,806	$ 2,770	$ 5,497