Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities:
Net income	$ 39,812	$ 29,472	$ 17,581
Adjustments to reconcile net income to cash provided by operating activities:
Increase in accrued interest receivable	(6,504)	(1,522)	(1,368)
Increase (decrease) in accrued interest payable	1,086	(129)	(448)
Provision for loan losses	871	1,379	782
Gain on sale of investments, net	(2,096)	(2,892)	(187)
Loss (gain) on non-recourse collateralized financing	(1,970)	561	(16)
Fair value adjustments, net	676	(294)	(205)
Amortization and depreciation	32,505	6,180	2,470
Stock-based compensation expense	917	626	527
Cash payments on stock appreciation rights	134	420	0
Net change in other assets and other liabilities	1,538	(1,768)	463
Net cash and cash equivalents provided by operating activities	70,641	30,071	19,631
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchase of investments	(1,606,819)	(1,112,804)	(508,109)
Principal payments received on investments	478,488	315,709	117,675
(Increase) decrease in principal receivable on investments	(10,087)	168	(2,604)
Proceeds from sales of investments	184,688	56,585	18,707
Principal payments received on securitized mortgage loans	37,556	54,977	29,084
Other investing activities	419	(297)	18
Net cash and cash equivalents used in investing activities	(915,755)	(685,662)	(345,229)
Financing activities:
Borrowings under repurchase agreements, net	859,610	595,854	364,112
Borrowings under non-recourse collateralized financing	0	50,678	0
Principal payments on non-recourse collateralized financing	(15,296)	(43,829)	(17,271)
Cash paid to redeem non-recourse collateralized financing	(23,669)	(56,406)	(15,493)
Decrease in restricted cash	0	0	2,974
Proceeds from issuance of common stock	95,282	116,850	12,873
Dividends paid	(40,873)	(18,893)	(15,759)
Net cash and cash equivalents provided by financing activities	875,054	644,254	331,436
Net increase (decrease) in cash and cash equivalents	29,940	(11,337)	5,838
Cash and cash equivalents at beginning of period	18,836	30,173	24,335
Cash and cash equivalents at end of period	48,776	18,836	30,173
Supplemental Disclosure of Cash Activities:
Cash paid for interest	$ 22,110	$ 14,568	$ 16,293