CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Net income (loss)	$ (2,625,664,000)	$ 1,923,591,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Amortization of premiums and discounts of investments, net	569,406,000	289,693,000
Amortization of securitized debt premiums and discounts and deferred financing costs	(11,020,000)	(202,000)
Depreciation, amortization and other noncash expenses	16,538,000	12,907,000
Net (gains) losses on disposals of investments	132,249,000	52,649,000
Net (gains) losses on investments and derivatives	2,245,397,000	(1,207,835,000)
Income from unconsolidated joint ventures	2,681,000	5,067,000
Loan loss provision	5,703,000	0
Payments on purchases of loans held for sale	(134,504,000)	(110,350,000)
Proceeds from sales and repayments of loans held for sale	113,835,000	46,721,000
Net receipts (payments) on derivatives	(2,051,618,000)	1,286,408,000
Net change in
Other assets	(20,707,000)	(98,456,000)
Interest receivable	(75,283,000)	759,000
Interest payable	120,399,000	225,371,000
Other liabilities	26,498,000	(136,273,000)
Net cash provided by (used in) operating activities	(1,686,090,000)	2,290,050,000
Cash flows from investing activities
Payments on purchases of Residential Securities	(43,574,404,000)	(7,309,307,000)
Proceeds from sales of Residential Securities	13,096,706,000	3,365,971,000
Principal payments on Residential Securities	6,062,830,000	5,664,811,000
Payments on purchases of MSRs	0	(381,000)
Payments on purchases of corporate debt	(250,247,000)	(464,496,000)
Proceeds from sales of corporate debt	235,131,000	0
Principal payments on corporate debt	87,242,000	226,723,000
Originations and purchases of commercial real estate investments	(438,218,000)	(358,179,000)
Proceeds from sales of commercial real estate investments	193,846,000	28,079,000
Principal repayments on commercial real estate investments	1,570,693,000	395,325,000
Proceeds from sales of real estate	6,661,000	0
Proceeds from reverse repurchase agreements	59,546,512,000	41,248,786,000
Payments on reverse repurchase agreements	(58,896,472,000)	(41,508,548,000)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	256,000	4,133,000
Payments on purchases of residential mortgage loans held for investment	(972,812,000)	(373,051,000)
Proceeds from repayments of residential mortgage loans held for investment	316,406,000	153,722,000
Net cash provided by (used in) investing activities	(23,015,870,000)	1,073,588,000
Cash flows from financing activities
Proceeds from repurchase agreements and other secured financing	2,807,924,726,000	2,727,664,289,000
Principal payments on repurchase agreements and other secured financing	(2,783,914,681,000)	(2,729,676,977,000)
Proceeds from issuances of securitized debt	1,614,580,000	279,203,000
Principal repayments on securitized debt	(1,497,815,000)	(488,335,000)
Payment of deferred financing cost	(4,524,000)	0
Net proceeds from stock offerings, direct purchases and dividend reinvestments	1,787,879,000	461,044,000
Redemptions of preferred stock	(55,000,000)	(412,500,000)
Principal payments on mortgages payable	(12,475,000)	0
Net contributions (distributions) from (to) noncontrolling interests	(779,000)	(706,000)
Dividends paid	(893,389,000)	(760,916,000)
Net cash provided by (used in) financing activities	24,948,522,000	(2,934,898,000)
Net (decrease) increase in cash and cash equivalents	246,562,000	428,740,000
Cash and cash equivalents including cash pledged as collateral, beginning of period	1,735,749,000	706,589,000
Cash and cash equivalents including cash pledged as collateral, end of period	1,982,311,000	1,135,329,000
Supplemental disclosure of cash flow information
Interest received	2,296,054,000	1,879,931,000
Dividends received	4,186,000	3,355,000
Interest paid (excluding interest paid on interest rate swaps)	1,277,824,000	740,186,000
Net interest paid on interest rate swaps	(190,108,000)	(141,772,000)
Taxes received (paid)	204,000	136,000
Noncash investing activities
Receivable for unsettled trades	5,322,000	21,728,000
Payable for unsettled trades	620,784,000	1,108,834,000
Net change in unrealized gains (losses) on available-for-sale securities, net of reclassification adjustment	3,344,868,000	(2,308,427,000)
Noncash financing activities
Dividends declared, not yet paid	$ 364,066,000	$ 349,300,000