Securitization Activities and Consolidation - Consolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 8,074		$ 5,189	$ 8,708	$ 7,273
Restricted cash and cash equivalents	1,790		991
Securities purchased under agreement to resell	99,252		56,271
Investments in securities, at fair value	71,702		75,711
Mortgage loans held-for-investment	2,189,656	$ 1,984,419	1,984,912
Accrued interest receivable, net	7,583		6,848
Other assets	40,051	22,992	22,799
Total assets	2,454,071		2,193,780
Accrued interest payable	6,020		6,559
Debt	2,423,316		2,169,685
Other Liabilities	10,231	$ 8,046	8,042
Total liabilities	2,440,180		2,184,658
Held by consolidated trusts
Variable Interest Entity [Line Items]
Cash and cash equivalents	1,490		870
Restricted cash and cash equivalents	1,489		869
Securities purchased under agreement to resell	50,546		23,137
Investments in securities, at fair value	1,734		597
Mortgage loans held-for-investment	2,115,509		1,940,523
Accrued interest receivable, net	6,954		6,170
Other assets	21,246		9,824
Total assets	2,197,479		1,981,121
Accrued interest payable	5,604		5,536
Debt	2,138,420		1,898,355
Other Liabilities	0		1
Total liabilities	$ 2,144,024		$ 1,903,892