CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Statement of Cash Flows [Abstract]
Net income (loss)	$ (3,372,833,000)	$ 2,309,020,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Amortization of premiums and discounts of investments, net	943,277,000	474,449,000
Amortization of securitized debt premiums and discounts and deferred financing costs	(11,457,000)	991,000
Depreciation, amortization and other noncash expenses	24,107,000	63,839,000
Net (gains) losses on disposals of investments	65,727,000	376,943,000
Net (gains) losses on investments and derivatives	2,589,685,000	(1,679,921,000)
Income from unconsolidated joint ventures	3,350,000	6,441,000
Loan loss provision	9,207,000	0
Payments on purchases of loans held for sale	(196,252,000)	(191,641,000)
Proceeds from sales and repayments of loans held for sale	220,409,000	64,460,000
Net receipts (payments) on derivatives	(2,561,170,000)	1,519,228,000
Net change in
Other assets	(45,547,000)	100,010,000
Interest receivable	(92,959,000)	(8,468,000)
Interest payable	(5,131,000)	124,316,000
Other liabilities	34,194,000	(136,510,000)
Net cash provided by (used in) operating activities	(2,395,393,000)	3,023,157,000
Cash flows from investing activities
Payments on purchases of Residential Securities	(51,291,188,000)	(17,053,068,000)
Proceeds from sales of Residential Securities	19,619,907,000	9,558,735,000
Principal payments on Residential Securities	11,163,622,000	8,696,239,000
Payments on purchases of MSRs	0	(381,000)
Payments on purchases of corporate debt	(631,275,000)	(744,071,000)
Proceeds from sales of corporate debt	265,218,000	0
Principal payments on corporate debt	143,284,000	235,423,000
Originations and purchases of commercial real estate investments	(618,348,000)	(697,753,000)
Proceeds from sales of commercial real estate investments	193,846,000	134,538,000
Principal repayments on commercial real estate investments	1,852,854,000	478,726,000
Proceeds from sales of real estate	6,661,000	0
Proceeds from reverse repurchase agreements	78,439,755,000	70,016,988,000
Payments on reverse repurchase agreements	(77,789,715,000)	(70,313,441,000)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	1,975,000	5,434,000
Payments on purchases of residential mortgage loans held for investment	(1,692,648,000)	(729,917,000)
Proceeds from repayments of residential mortgage loans held for investment	570,503,000	251,407,000
Cash paid related to asset acquisition, net of cash acquired	0	(258,334,000)
Net cash provided by (used in) investing activities	(19,765,549,000)	(419,475,000)
Cash flows from financing activities
Proceeds from repurchase agreements and other secured financing	4,275,937,246,000	3,866,183,872,000
Principal payments on repurchase agreements and other secured financing	(4,254,088,297,000)	(3,868,097,943,000)
Proceeds from issuances of securitized debt	2,030,356,000	588,111,000
Principal repayments on securitized debt	(1,778,314,000)	(614,536,000)
Payment of deferred financing cost	(5,222,000)	0
Net proceeds from stock offerings, direct purchases and dividend reinvestments	1,829,025,000	1,531,690,000
Redemptions of preferred stock	(230,000,000)	(412,500,000)
Principal payments on mortgages payable	(25,398,000)	(49,000)
Net contributions (distributions) from (to) noncontrolling interests	(987,000)	(780,000)
Net payment on share repurchase	(155,304,000)	0
Dividends paid	(1,293,991,000)	(1,405,389,000)
Net cash provided by (used in) financing activities	22,219,114,000	(2,227,524,000)
Net (decrease) increase in cash and cash equivalents	58,172,000	376,158,000
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	1,793,921,000	1,082,747,000
Supplemental disclosure of cash flow information
Interest received	3,583,189,000	2,846,535,000
Dividends received	6,279,000	5,448,000
Interest paid (excluding interest paid on interest rate swaps)	2,041,539,000	1,159,384,000
Net interest paid on interest rate swaps	(96,169,000)	(243,946,000)
Taxes received (paid)	274,000	86,000
Noncash investing activities
Receivable for unsettled trades	193,229,000	1,266,840,000
Payable for unsettled trades	245,626,000	2,505,428,000
Net change in unrealized gains (losses) on available-for-sale securities, net of reclassification adjustment	4,293,680,000	(2,696,936,000)
Noncash financing activities
Dividends declared, not yet paid	$ 359,491,000	$ 102,811,000