Consolidated Balance Sheets (USD $)	Sep. 30, 2012		Dec. 31, 2011
Assets:
Residential mortgage investments($13.93 and $11.93 billion pledged under repurchase arrangements at September 30, 2012 and December 31, 2011, respectively)	$ 14,313,208,000	[1]	$ 12,264,906,000	[1]
Cash collateral receivable from interest rate swap counterparties	57,737,000		48,505,000
Interest rate swap agreements at fair value	24,000		617,000
Cash and cash equivalents	500,741,000		426,717,000
Receivables and other assets	140,727,000		100,760,000
Investments in unconsolidated affiliates	3,117,000		3,117,000
Assets, total	15,015,554,000		12,844,622,000
Liabilities:
Repurchase arrangements and similar borrowings	13,250,488,000		11,352,444,000
Interest rate swap agreements at fair value	41,199,000		31,348,000
Unsecured borrowings	103,095,000		103,095,000
Common stock dividend payable	36,173,000		38,184,000
Accounts payable and accrued expenses	20,772,000		26,844,000
Liabilities, total	13,451,727,000		11,551,915,000
Stockholders' equity:
Common stock-$0.01 par value; 250,000 shares authorized: 98,956 and 88,287 shares issued and outstanding at September 30, 2012 and December 31, 2011, respectively	990,000		883,000
Paid-in capital	1,400,514,000		1,257,653,000
Accumulated deficit	(354,883,000)		(354,883,000)
Accumulated other comprehensive income	328,214,000		204,540,000
Stockholders' Equity Attributable to Parent	1,563,827,000		1,292,707,000
Liabilities and Equity, Total	15,015,554,000		12,844,622,000
Convertible Preferred Stock [Member] | $1.60 Cumulative Preferred Stock, Series A [Member]
Stockholders' equity:
Cumulative Convertible Preferred Stock	2,604,000		2,605,000
Convertible Preferred Stock [Member] | $1.26 Cumulative Convertible Preferred Stock, Series B [Member]
Stockholders' equity:
Cumulative Convertible Preferred Stock	$ 186,388,000		$ 181,909,000

[1] Includes unrealized gains and losses for residential mortgage investments classified as available-for-sale (see NOTE 8).