Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 7,023	$ 33,893	$ 43,099
Adjustments to reconcile net income to cash provided by operating activities:
(Increase) decrease in accrued interest receivable	(1,200)	577	2,368
Increase (decrease) in accrued interest payable	6,574	578	1,413
Loss (gain) on derivative instruments, net	3,461	(3,044)	5,606
Loss on sale of investments, net	(23,373)	(11,530)	(4,238)
Fair value adjustments, net	(52)	(75)	(103)
Amortization of investment premiums, net	143,036	157,706	150,729
Other amortization and depreciation, net	1,232	1,287	1,502
Stock-based compensation expense	1,231	1,954	2,709
Change in other assets and liabilities, net	(4,118)	42	(1,047)
Net cash and cash equivalents provided by operating activities	180,560	204,448	210,514
Investing activities:
Purchase of investments	(1,789,272)	(1,317,959)	(435,046)
Principal payments received on investments	188,898	307,133	448,567
Proceeds from sales of investments	733,064	1,073,093	99,284
Principal payments received on mortgage loans held for investment, net	4,210	3,386	4,953
Proceeds from Limited Partnership Investments	0	0	10,835
Net receipts on derivatives, including terminations	(6,135)	21,986	(60,588)
Other investing activities	(102)	(206)	(37)
Net cash and cash equivalents (used in) provided by investing activities	(869,337)	87,433	67,968
Financing activities:
Borrowings under repurchase agreements	105,236,233	84,876,542	40,594,639
Repayments of repurchase agreement borrowings	(104,534,151)	(85,209,592)	(40,805,107)
Principal payments on non-recourse collateralized financing	(2,094)	(938)	(2,039)
Proceeds from issuance of preferred stock	1,599	31,350	548
Proceeds from issuance of common stock	41,858	47,182	137
Cash paid for stock issuance costs	(10)	(61)	(201)
Payments for Repurchase of Common Stock			(310)
Payments related to tax withholding for stock-based compensation	(364)	(521)	(485)
Dividends paid	(52,790)	(47,532)	(51,900)
Net cash and cash equivalents provided by (used in) financing activities	690,281	(303,570)	(264,718)
Net increase (decrease) in cash, cash equivalents, and restricted cash	1,504	(11,689)	13,764
Cash, cash equivalents, and restricted cash at beginning of period	87,200	98,889	85,125
Cash, cash equivalents, and restricted cash at end of period	88,704	87,200	98,889
Supplemental Disclosure of Cash Activity:
Cash paid for interest	$ 53,205	$ 35,851	$ 24,033