Consolidated Balance Sheets (USD $)	Jun. 30, 2012		Dec. 31, 2011
Assets:
Residential mortgage investments ($13.38 and $11.93 billion pledged under repurchase arrangements at June 30, 2012 and December 31, 2011, respectively)	$ 13,799,487,000	[1]	$ 12,264,906,000	[1]
Cash collateral receivable from interest rate swap counterparties	55,758,000		48,505,000
Interest rate swap agreements at fair value			617,000
Cash and cash equivalents	433,241,000		426,717,000
Receivables and other assets	118,962,000		100,760,000
Investments in unconsolidated affiliates	3,117,000		3,117,000
Assets, total	14,410,565,000		12,844,622,000
Liabilities:
Repurchase arrangements and similar borrowings	12,728,797,000		11,352,444,000
Interest rate swap agreements at fair value	37,874,000		31,348,000
Unsecured borrowings	103,095,000		103,095,000
Common stock dividend payable	39,427,000		38,184,000
Accounts payable and accrued expenses	20,920,000		26,844,000
Liabilities, total	12,930,113,000		11,551,915,000
Stockholders' equity:
Common stock - $0.01 par value; 250,000 shares authorized: 97,456 and 88,287 shares issued and outstanding at June 30, 2012 and December 31, 2011, respectively	975,000		883,000
Paid-in capital	1,380,445,000		1,257,653,000
Accumulated deficit	(354,883,000)		(354,883,000)
Accumulated other comprehensive income	264,923,000		204,540,000
Stockholders' Equity Attributable to Parent	1,480,452,000		1,292,707,000
Liabilities and Equity, Total	14,410,565,000		12,844,622,000
$1.60 Cumulative Preferred Stock, Series A [Member]
Stockholders' equity:
$1.26 Cumulative Convertible Preferred Stock, Series B, 16,493 and 16,184 shares issued and outstanding ($187,692 and $184,175 aggregate liquidation preference) at June 30, 2012 and December 31, 2011, respectively	2,604,000		2,605,000
$1.26 Cumulative Convertible Preferred Stock, Series B [Member]
Stockholders' equity:
$1.26 Cumulative Convertible Preferred Stock, Series B, 16,493 and 16,184 shares issued and outstanding ($187,692 and $184,175 aggregate liquidation preference) at June 30, 2012 and December 31, 2011, respectively	$ 186,388,000		$ 181,909,000

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