Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Residential mortgage investments	$ 13,450,000	$ 11,930,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000	250,000
Common stock, shares issued	96,229	88,287
Common stock, shares outstanding	96,229	88,287
$1.60 Cumulative Preferred Stock, Series A [Member]
Preferred stock, dividend rate	$ 1.60	$ 1.60
Preferred stock, shares issued	186	186
Preferred stock, shares outstanding	186	186
Preferred stock, aggregate liquidation preference	3,054	3,056
Preferred Stock [Member]
Preferred stock, par value	$ 0.10	$ 0.10
Preferred stock, shares authorized	100,000	100,000
Convertible Preferred Stock [Member] | $1.26 Cumulative Convertible Preferred Stock, Series B [Member]
Preferred stock, dividend rate	$ 1.26	$ 1.26
Preferred stock, shares issued	16,493	16,184
Preferred stock, shares outstanding	16,493	16,184
Preferred stock, aggregate liquidation preference	$ 187,692	$ 184,175