CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Cash Flows From Operating Activities:
Net income	$ 411,637	$ 524,668	$ 551,943
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Accretion) amortization of investment discounts/premiums, net	28,633	(25,422)	(3,127)
Accretion (amortization) of deferred financing costs and securitized debt discounts/premiums, net	(13,124)	7,395	1,543
Amortization of swaption premium	1,476	6,269	6,559
Net unrealized losses (gains) on derivatives	141,162	(47,976)	(50,093)
Margin (paid) received on derivatives	(320,899)	31,442	56,050
Net unrealized losses (gains) on financial instruments at fair value	(46,632)	(111,410)	(59,552)
Net realized losses (gains) on sales of investments	2,743	(9,123)	(18,155)
Net other-than-temporary credit impairment losses	21,791	61,856	57,987
(Gain) loss on extinguishment of debt	(26,376)	35,274	477
Equity-based compensation expense	8,797	3,614	2,204
Changes in operating assets:
Decrease (increase) in accrued interest receivable, net	(22,652)	(21,091)	(13,450)
Decrease (increase) in other assets	63,235	18,080	3,994
Changes in operating liabilities:
Increase (decrease) in accounts payable and other liabilities	(722)	498	5,290
Increase (decrease) in accrued interest payable, net	48,515	13,217	11,237
Net cash provided by (used in) operating activities	297,584	487,291	552,907
Cash Flows From Investing Activities:
Acquisition of investments in consolidated VIEs	0	(398,261)	0
Net cash provided by (used in) investing activities	(6,026,067)	(4,331,009)	(1,270,560)
Cash Flows From Financing Activities:
Proceeds from repurchase agreements	71,279,975	44,120,574	34,202,707
Payments on repurchase agreements	(64,499,287)	(42,471,025)	(36,041,143)
Net proceeds from preferred stock offerings	251,536	314,429	140,065
Payments on repurchase of common stock	(14,834)	0	0
Proceeds from securitized debt borrowings, collateralized by loans held for investment	1,769,539	5,152,469	4,797,255
Payments on securitized debt borrowings, collateralized by loans held for investment	(2,613,038)	(2,844,132)	(1,668,670)
Payments on securitized debt borrowings, collateralized by Non-Agency RMBS	(43,898)	(131,039)	(194,634)
Common dividends paid	(374,396)	(375,771)	(454,275)
Preferred dividends paid	(43,197)	(35,932)	0
Net cash provided by (used in) financing activities	5,712,400	3,729,573	781,305
Net increase (decrease) in cash and cash equivalents	(16,083)	(114,145)	63,652
Cash and cash equivalents at beginning of period	63,569	177,714	114,062
Cash and cash equivalents at end of period	47,486	63,569	177,714
Supplemental disclosure of cash flow information:
Interest received	1,279,297	1,092,245	917,491
Interest paid	643,717	512,133	335,077
Non-cash investing activities:
Payable for investments purchased	1,136,157	567,440	520,532
Net change in unrealized gain (loss) on available-for sale securities	(170,070)	78,796	(55,685)
Retained beneficial interests	39,844	0	0
Acquisition of securities in Consolidated VIEs
Securitized loans held for investment, at fair value	0	419,222	0
Securitized debt at fair value	0	(20,961)	0
Non-cash financing activities:
Dividends declared, not yet paid	95,986	95,365	94,557
Preferred dividends accrued	0	0	2,449
Agency MBS portfolio
Cash Flows From Investing Activities:
Purchases	(7,917,661)	(1,326,178)	(1,040,290)
Sales	16,184	743,937	2,570,025
Principal payments	524,989	423,506	649,961
Non-agency RMBS Portfolio
Cash Flows From Investing Activities:
Purchases	(133,247)	(15,262)	(203,400)
Sales	19,928	5,045	95,399
Principal payments	521,109	568,339	532,701
Loans held for investment
Cash Flows From Investing Activities:
Sales	754,806	0	0
Principal payments	1,859,155	1,788,408	1,022,414
Purchases	$ (1,671,330)	$ (6,120,543)	$ (4,897,370)