Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income (loss)	$ 27,806	$ 68,069	$ 74,042
Adjustments to reconcile net income to cash provided by operating activities:
Decrease (increase) in accrued interest receivable	546	1,370	(10,464)
(Decrease) increase in accrued interest payable	(600)	(347)	730
Provision for loan losses	0	261	192
Loss (gain) on derivative instruments, net	53,393	10,076	908
Loss (gain) on sale of investments, net	(16,223)	(3,354)	(8,461)
Fair value adjustments, net	(208)	652	(735)
Amortization of investment premiums, net	137,837	128,865	91,622
Other amortization and depreciation	8,900	7,743	(1,092)
Stock-based compensation expense	2,719	2,314	1,712
Other operating activities	381	(6,889)	934
Net cash and cash equivalents provided by operating activities	214,551	208,760	149,388
Investing activities:
Purchase of investments	(599,381)	(1,419,060)	(2,639,909)
Principal payments received on investments	518,303	913,210	679,635
Proceeds from sales of investments	503,918	358,090	231,145
Principal payments received on mortgage loans held for investment, net	16,787	15,828	40,830
Investment in limited partnership	(4,000)	0	0
Net payments on derivatives not designated as hedges	11,415	39,097	0
Other investing activities	(7)	5,891	(2,893)
Net cash and cash equivalents used in investing activities	424,205	(165,138)	(1,691,192)
Financing activities:
(Repayments of) borrowings under repurchase agreements, net	(567,887)	16,209	1,470,170
Principal payments on non-recourse collateralized financing	(2,167)	(17,840)	(40,626)
Increase in restricted cash	(28,878)	(13,346)	0
Proceeds from issuance of preferred stock	0	54,251	55,407
Proceeds from issuance of common stock	177	7,436	123,868
Cash paid for repurchases of common stock	0	(6,934)	(921)
Payments Related to tax withholding for share-based compensation	(507)	(545)	0
Dividends paid	(64,880)	(69,332)	(59,061)
Net cash and cash equivalents provided by (used in) financing activities	(664,142)	(30,101)	1,548,837
Net increase (decrease) in cash and cash equivalents	(25,386)	13,521	7,033
Cash and cash equivalents at beginning of period	69,330	55,809	48,776
Cash and cash equivalents at end of period	43,944	69,330	55,809
Supplemental Disclosure of Cash Activities:
Cash paid for interest	$ 19,445	$ 33,517	$ 34,035