Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 3,267	$ 1,446
Operating activities:
Net income (loss)	(2,421)	265
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of premiums and discounts on mortgage-backed securities, net	384	142
Stock based compensation	3	2
Gain on sale of investment securities, net	(494)	(60)
Unrealized gain on investment securities measured at fair value through net income, net	(197)	(1,060)
Loss on derivative instruments and other securities, net	3,154	1,000
(Increase) decrease in other assets	78	(35)
Increase (decrease) in accounts payable and other accrued liabilities	(160)	75
Net cash provided by operating activities	347	329
Investing activities:
Purchases of Agency mortgage-backed securities	(23,339)	(16,038)
Purchases of credit risk transfer and non-Agency securities	(347)	(499)
Proceeds from sale of Agency mortgage-backed securities	49,596	4,694
Proceeds from sale of credit risk transfer and non-Agency securities	492	297
Principal collections on Agency mortgage-backed securities	3,743	1,889
Principal collections on credit risk transfer and non-Agency securities	11	5
Payments on U.S. Treasury securities	(17,907)	(7,550)
Proceeds from U.S. Treasury securities	8,795	5,103
Net proceeds from reverse repurchase agreements	5,275	1,526
Net payments on derivative instruments	(2,742)	(714)
Net cash provided by (used in) investing activities	23,577	(11,287)
Financing activities:
Proceeds from repurchase arrangements	1,162,934	930,289
Payments on repurchase agreements	(1,185,576)	(919,321)
Payments on debt of consolidated variable interest entities	(16)	(13)
Net proceeds from preferred stock issuance	(557)	(227)
Net proceeds from common stock issuance	439	0
Cash dividends paid	(277)	(298)
Net cash provided by (used in) financing activities	(21,939)	10,884
Net change in cash and cash equivalents	1,985	$ (74)
Cash and cash equivalents at end of period	$ 1,289