CONSOLIDATED STATEMENTS OF CASH FLOWS	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Statement of Cash Flows [Abstract]
Net income (loss)	$ (2,163,091,000)	$ 54,148,000	$ 1,569,016,000
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Amortization of premiums and discounts of investments, net	1,113,273,000	692,811,000	872,346,000
Amortization of securitized debt premiums and discounts and deferred financing costs	(11,854,000)	(3,439,000)	(3,596,000)
Depreciation, amortization and other noncash expenses	31,559,000	72,364,000	27,956,000
Net (gains) losses on disposals of investments	47,944,000	1,123,969,000	3,938,000
Net (gains) losses on investments and derivatives	1,855,025,000	136,673,000	(734,672,000)
Income from unconsolidated joint ventures	6,893,000	2,840,000	2,864,000
Loan loss provision	16,569,000	3,496,000	0
Payments on purchases of loans held for sale	(250,348,000)	(227,871,000)	(309,473,000)
Proceeds from sales and repayments of loans held for sale	282,693,000	97,913,000	410,285,000
Net receipts (payments) on derivatives	(1,939,634,000)	480,216,000	(233,915,000)
Net change in
Due to / from brokers	0	0	(16,000)
Other assets	(39,880,000)	98,104,000	(58,715,000)
Interest receivable	(85,951,000)	(19,563,000)	(52,202,000)
Interest payable	(94,593,000)	295,640,000	89,777,000
Other liabilities	31,838,000	(185,283,000)	48,646,000
Net cash provided by (used in) operating activities	(1,199,557,000)	2,622,018,000	1,632,239,000
Cash flows from investing activities
Payments on purchases of Residential Securities	(62,794,871,000)	(44,624,006,000)
Payments on purchases of Residential Securities			(40,287,765,000)
Proceeds from sales of Residential Securities	25,513,227,000	33,256,888,000
Proceeds from sales of Residential Securities			13,402,428,000
Principal payments on Residential Securities	17,156,148,000	11,365,683,000	12,016,190,000
Payments on purchases of MSRs	0	(381,000)	(11,493,000)
Proceeds from sales of MSRs	0	0	33,000
Payments on purchases of corporate debt	(890,042,000)	(1,241,818,000)	(693,095,000)
Proceeds from sales of corporate debt	265,218,000	0	0
Principal payments on corporate debt	368,927,000	378,865,000	462,622,000
Originations and purchases of commercial real estate investments	(1,299,047,000)	(815,252,000)	(504,952,000)
Proceeds from sales of commercial real estate investments	193,846,000	150,059,000	11,960,000
Principal repayments on commercial real estate investments	1,968,621,000	1,504,032,000	1,669,900,000
Proceeds from sales of real estate	24,955,000		0
Proceeds from reverse repurchase agreements	98,339,755,000	85,318,562,000	67,675,100,000
Payments on reverse repurchase agreements	(97,689,715,000)	(85,030,351,000)	(67,675,100,000)
Distributions in excess of cumulative earnings from unconsolidated joint ventures	3,155,000	26,228,000	7,998,000
Payments on purchases of residential mortgage loans held for investment	(2,647,129,000)	(1,286,046,000)	(928,512,000)
Proceeds from repayments of residential mortgage loans held for investment	845,281,000	347,451,000	185,391,000
Payments on purchases of equity securities	0	0	(2,104,000)
Cash paid related to asset acquisition, net of cash acquired	0	(258,334,000)	0
Net payment from disposal of subsidiary	0	0	5,451,000
Net cash provided by (used in) investing activities	(20,641,671,000)	(908,420,000)	(14,665,948,000)
Cash flows from financing activities
Proceeds from repurchase agreements and other secured financing	5,470,733,256,000	5,117,155,986,000	3,606,915,741,000
Principal payments on repurchase agreements and other secured financing	(5,449,836,013,000)	(5,116,952,444,000)	(3,594,482,419,000)
Proceeds from issuances of securitized debt	3,444,055,000	920,142,000	0
Principal repayments on securitized debt	(2,031,959,000)	(1,384,333,000)	(1,022,994,000)
Payment of deferred financing cost	(12,228,000)	(1,072,000)	(2,054,000)
Principal payments on participation sold	0	0	(12,827,000)
Principal payments on mortgages payable	(26,202,000)	(716,000)	(2,365,000)
Net contributions (distributions) from (to) noncontrolling interests	(1,136,000)	(971,000)	(1,104,000)
Net proceeds from stock offerings, direct purchases and dividend reinvestments	1,829,025,000	1,532,356,000	2,347,058,000
Redemptions of preferred stock	(230,000,000)	(412,500,000)	(185,312,000)
Net payments on share repurchases	(223,574,000)	0	0
Dividends paid	(1,689,016,000)	(1,540,886,000)	(1,353,172,000)
Net cash provided by (used in) financing activities	21,956,208,000	(684,438,000)	12,200,552,000
Net (decrease) increase in cash and cash equivalents	114,980,000	1,029,160,000	(833,157,000)
Cash and cash equivalents including cash pledged as collateral, beginning of period	1,735,749,000	706,589,000	1,539,746,000
Cash and cash equivalents including cash pledged as collateral, end of period	1,850,729,000	1,735,749,000	706,589,000
Supplemental disclosure of cash flow information
Interest received	4,811,218,000	3,894,478,000	3,447,308,000
Dividends received	8,395,000	7,564,000	5,238,000
Interest paid (excluding interest paid on interest rate swaps)	2,902,644,000	1,726,887,000	987,958,000
Net interest received (paid) on interest rate swaps	(323,028,000)	(1,894,000)	369,660,000
Taxes received (paid)	2,284,000	(295,000)	(1,502,000)
Noncash investing activities
Receivable for unsettled trades	4,792,000	68,779,000	1,232,000
Payable for unsettled trades	463,387,000	583,036,000	656,581,000
Net change in unrealized gains (losses) on available-for-sale securities, net of reclassification adjustment	4,118,056,000	(853,845,000)	(40,127,000)
Noncash financing activities
Dividends declared, not yet paid	357,527,000	394,129,000	347,876,000
Securitized debt assumed through consolidation of VIEs	$ 874,694,000	$ 0	$ 315,111,000