Securitization Activities and Consolidation - Consolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity, Consolidated, Carrying Amount, Assets [Abstract]
Cash and cash equivalents	$ 24,324		$ 5,189	$ 6,239	$ 7,273
Restricted cash and cash equivalents	17,920		991
Securities purchased under agreement to resell	45,968		56,271
Investments in securities, at fair value	79,189		75,711
Mortgage loans held-for-investment	2,014,155	$ 1,984,419	1,984,912
Accrued interest receivable (Notes 3, 4, 7, 10)	6,841		6,848
Other assets	31,561	22,992	22,799
Total assets	2,241,984		2,193,780
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities [Abstract]
Accrued interest payable	6,271		6,559
Debt	2,216,135		2,169,685
Other Liabilities	7,848	$ 8,046	8,042
Total liabilities	2,232,480		2,184,658
Held by consolidated trusts
Variable Interest Entity, Consolidated, Carrying Amount, Assets [Abstract]
Cash and cash equivalents	17,856		870
Restricted cash and cash equivalents	17,855		869
Securities purchased under agreement to resell	13,510		23,137
Investments in securities, at fair value	1,536		597
Mortgage loans held-for-investment	1,963,630		1,940,523
Accrued interest receivable (Notes 3, 4, 7, 10)	6,181		6,170
Other assets	14,332		9,824
Total assets	2,017,045		1,981,121
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities [Abstract]
Accrued interest payable	5,551		5,536
Debt	1,930,005		1,898,355
Other Liabilities	0		1
Total liabilities	$ 1,935,556		$ 1,903,892