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	$ 163,626	$ 160,204	$ 126,896
Noncash items:
Amortization of investment premiums	96,677	68,077	57,634
Depreciation and other amortization	195	206	220
Amortization of equity-based awards	2,236	1,821	1,525
Incentive compensation paid in common shares	2,799	1,446
Change in measureable hedge ineffectiveness related to interest rate swap agreements	(411)	306	(722)
Impairment related to real estate held for sale		470	106
Gain on asset sales	(273)	(114)	(277)
Net change in receivables, other assets, accounts payable and accrued expenses	(919)	5,297	6,989
Net cash provided by operating activities	263,930	237,713	192,371
Investing activities:
Purchases of residential mortgage investments	(4,384,866)	(5,899,041)	(3,414,143)
Interest receivable acquired with the purchase of residential mortgage investments	(7,180)	(12,099)	(6,616)
Proceeds from asset sales	2,010	10,786	4,131
Principal collections on residential mortgage investments	2,756,772	2,110,334	2,928,486
Principal collections on commercial loan investments			10,000
Net cash used in investing activities	(1,633,264)	(3,790,020)	(478,142)
Financing activities:
Proceeds from repurchase arrangements and similar borrowings	127,808,676	88,814,514	69,438,636
Principal payments on repurchase arrangements and similar borrowings	(126,376,876)	(85,254,811)	(69,081,148)
Increase in cash collateral receivable from interest rate swap counterparties	(1,467)	(13,216)	(4,804)
(Decrease) increase in cash collateral payable to interest rate swap counterparties		(9,024)	9,024
Equity capital issuances	145,929	236,811	10,233
Common share repurchases	(35,062)
Dividends paid	(173,138)	(154,840)	(136,203)
Net cash provided by financing activities	1,368,062	3,619,434	235,738
Net change in cash and cash equivalents	(1,272)	67,127	(50,033)
Cash and cash equivalents at beginning of year	426,717	359,590	409,623
Cash and cash equivalents at end of year	$ 425,445	$ 426,717	$ 359,590