Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net income	$ 74,042	$ 39,812	$ 29,472
Adjustments to reconcile net income to cash provided by operating activities:
Increase in accrued interest receivable	(10,464)	(6,504)	(1,522)
(Decrease) increase in accrued interest payable	730	1,086	(129)
Provision for loan losses	192	871	1,379
Marketable Securities, Realized Gain (Loss)	8,461	2,096	2,891
Loss on non-recourse collateralized financing	0	1,970	(561)
Fair value adjustments, net	173	676	(294)
Amortization and depreciation	90,530	32,505	6,180
Stock-based compensation expense	1,828	917	626
Cash paid for stock appreciation rights	(116)	(134)	(420)
Net change in other assets and other liabilities	934	1,538	(1,769)
Net cash and cash equivalents provided by operating activities	149,388	70,641	30,071
Investing activities:
Purchase of investments	(2,639,909)	(1,606,819)	(1,112,804)
Principal payments received on investments	682,817	478,488	315,709
Increase in principal receivable on investments	(3,182)	(10,087)	168
Proceeds from sales of investments	231,145	184,688	56,585
Principal payments received on securitized mortgage loans	40,830	37,556	54,977
Other investing activities	(2,893)	419	(297)
Net cash and cash equivalents used in investing activities	(1,691,192)	(915,755)	(685,662)
Financing activities:
Borrowings under repurchase agreements, net	1,470,995	859,610	595,854
Deferred borrowing costs paid	(825)	0	0
Borrowings under non-recourse collateralized financing	0	0	50,678
Principal payments on non-recourse collateralized financing	(40,626)	(15,296)	(43,829)
Cash paid to redeem securitization financing bonds	0	(23,669)	(56,406)
Proceeds from issuance of preferred stock	55,407	0	0
Proceeds from issuance of stock	123,868	95,282	116,850
Cash paid for common stock repurchase	(921)	0	0
Dividends paid	(59,061)	(40,873)	(18,893)
Net cash and cash equivalents provided by financing activities	1,548,837	875,054	644,254
Net increase in cash and cash equivalents	7,033	29,940	(11,337)
Cash and cash equivalents at beginning of period	48,776	18,836	30,173
Cash and cash equivalents at end of period	55,809	48,776	18,836
Supplemental Disclosure of Cash Activities:
Cash paid for interest	$ 34,035	$ 22,110	$ 14,568