Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Statement of Cash Flows [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 2,165,000	$ 1,659,000
Operating activities:
Net income (loss)	(1,703,000)	(179,000)
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of premiums and discounts on mortgage-backed securities, net	607,000	325,000
Stock based compensation	7,000	5,000
Gain on sale of investment securities, net	(647,000)	(192,000)
Unrealized gain on investment securities measured at fair value through net income, net	(876,000)	(1,819,000)
Loss on derivative instruments and other securities, net	3,539,000	2,438,000
(Increase) decrease in other assets	59,000	(36,000)
Increase (decrease) in accounts payable and other accrued liabilities	(210,000)	22,000
Net cash provided by operating activities	776,000	564,000
Investing activities:
Purchases of Agency mortgage-backed securities	(39,715,000)	(23,963,000)
Purchases of credit risk transfer and non-Agency securities	(396,000)	(904,000)
Proceeds from sale of Agency mortgage-backed securities	54,967,000	12,186,000
Proceeds from sale of credit risk transfer and non-Agency securities	536,000	852,000
Principal collections on Agency mortgage-backed securities	7,867,000	4,772,000
Principal collections on credit risk transfer and non-Agency securities	49,000	14,000
Payments on U.S. Treasury securities	(19,793,000)	(22,535,000)
Proceeds from U.S. Treasury securities	16,206,000	7,122,000
Net proceeds from reverse repurchase agreements	2,270,000	13,219,000
Net payments on derivative instruments	(2,682,000)	(1,539,000)
Net cash provided by (used in) investing activities	19,309,000	(10,776,000)
Financing activities:
Proceeds from repurchase arrangements	2,166,205,000	1,904,071,000
Payments on repurchase agreements	(2,185,702,000)	(1,893,522,000)
Payments on debt of consolidated variable interest entities	(29,000)	(28,000)
Net proceeds from preferred stock issuance	(557,000)	(227,000)
Net proceeds from common stock issuance	439,000	190,000
Payments for common stock repurchases	(147,000)	0
Cash dividends paid	(525,000)	(587,000)
Net cash provided by (used in) financing activities	(19,202,000)	10,351,000
Net change in cash and cash equivalents	883,000	$ 139,000
Cash and cash equivalents at end of period	$ 859,000