CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Activities:
Net (loss) income	$ (17,492)	$ (47,700)	$ (19,970)	$ 17,365	$ 14,933	$ (2,853)	$ (85,162)	$ 29,445
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation on rental properties	120			118			359	355
Realized (gain) loss on sales of available-for-sale MBS	(214)			(799)			5,443	11,188
Unrealized gain (loss) on Agency MBS held as trading investments	(1,900)			(3,000)			(17,800)	14,600
Impairment charge	1,145			141			1,751	1,898
Gain on sale of residential properties				(30)				(30)
Amortization of restricted stock	25			25			74	74
Recovery on Non-Agency MBS								(1)
Net settlements received (paid) on interest rate swaps, net of amortization	2,092			3,055			11,350	4,715
Unrealized loss (gain) on interest rate swaps, net	28,720			(15,910)			120,146	(55,160)
Loss (gain) on derivatives	24,734			(13,090)			105,565	(36,433)
Changes in assets and liabilities:
Decrease in reverse repurchase agreements							20,000
(Increase) decrease in interest receivable	67			(267)			1,234	206
(Increase) decrease in prepaid expenses and other	(6,751)			189			(10,260)	258
(Decrease) in accrued interest payable	(4,040)			(5,535)			(6,231)	716
Increase in accrued expenses	2,026			23,823			6,183	30,473
Net cash provided by operating activities	7,281			37,092			63,195	91,369
Investing Activities:
Proceeds from sales, MBS portfolios	63,270			35,324			2,303,025	624,397
Purchases, MBS portfolios	(350,920)			(309,023)			(2,281,408)	(1,033,282)
Principal payments, MBS portfolios	214,797			250,604			649,334	719,716
Purchases, Residential mortgage loans held-for-securitization	(35,402)						(145,838)
Principal payments, Residential mortgage loans held-for-securitization	11,619						16,095
Residential properties purchases	(80)			15			(300)	(65)
Net cash provided by investing activities	(96,686)			(23,051)			540,998	310,851
Financing Activities:
Borrowings from repurchase agreements	7,394,951			5,565,241			21,926,918	18,058,298
Repayments on repurchase agreements	(7,295,692)			(5,569,901)			(22,483,443)	(18,410,173)
Borrowings from warehouse line of credit	30,898						126,620
Repayments on warehouse line of credit	(11,243)						(14,266)
Net settlements on TBA Agency MBS Contracts	5,084			593			20,093	(18,502)
Termination of de-designated interest rate swaps	(27,661)						(38,046)
Derivative counterparty margin	(604)
Proceeds from common stock issued	330			389			1,088	1,185
Preferred stock dividends paid	(2,297)			(2,297)			(6,892)	(6,872)
Common stock dividends paid	(10,855)			(13,763)			(36,471)	(43,215)
Net cash (used in) provided by financing activities	82,911			(19,738)			(504,717)	(418,754)
Net increase (decrease) in cash and cash equivalents	(6,494)			(5,697)			99,476	(16,534)
Cash, cash equivalents and restricted cash at beginning of period		$ 139,431	33,461		$ 12,593	23,430	33,461	23,430	$ 23,430
Cash, cash equivalents and restricted cash at end of period	132,937		$ 139,431	6,896		$ 12,593	132,937	6,896	$ 33,461
Supplemental Disclosure of Cash Flow Information:
Cash paid for interest	27,099			27,026			76,405	61,187
Change in payable for MBS purchased	43,290			2,611			43,290	2,611
Change in payables for residential mortgage loans purchased	(6,085)
Residential mortgage loans
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of premium (discount)	(29)			(28)			(87)	(84)
Impairment charge								18
Investing Activities:
Principal payments, Residential mortgage loans held-for-investment	30			29			90	85
Residential loans
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of premium (discount)	96						112
Agency MBS
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of premium (discount)	6,353			7,489			19,787	21,444
Realized (gain) loss on sales of available-for-sale MBS	(214)			(799)			5,488	11,188
Realized loss on sales of Agency MBS held as trading investments				231			7,128	7,558
Unrealized gain (loss) on Agency MBS held as trading investments	(1,939)			3,017			(17,834)	14,584
Investing Activities:
Proceeds from sales, MBS portfolios	59,600			35,300			2,300,000	618,500
Non-Agency MBS
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of premium (discount)	1,088			1,388			3,784	4,985
Impairment charge	1,145			141			1,751	1,898
Investing Activities:
Proceeds from sales, MBS portfolios	3,700						23,700
Series C Preferred Stock
Financing Activities:
Proceeds on Series C Preferred Stock issued							(318)	525
TBA Agency MBS
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Loss (gain) on derivatives	$ (3,986)			$ 2,820			$ (14,582)	$ 18,727