Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Pledged MBS	$ 4,013,556	$ 3,967,134
Common stock, par value	$ 0.01	$ 0.01
Common Stock, Shares Authorized	100,000,000	100,000,000
Common Stock, Shares, Issued	54,426,049	54,268,915
Common stock, shares outstanding	54,426,049	54,268,915
Series A Preferred Stock [Member]
ASSETS
Preferred Stock, Par Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	8,000,000	8,000,000
Preferred Stock, Shares Issued	2,300,000	2,300,000
Preferred Stock, Shares Outstanding	2,300,000	2,300,000
Preferred Stock, aggregate liquidation preference	57,500	57,500
Series B Preferred Stock [Member]
ASSETS
Preferred Stock, Par Value Per Share	$ 0.01	$ 0
Preferred Stock, Shares Authorized	7,000,000	0
Preferred Stock, Shares Issued	2,250,000	0
Preferred Stock, Shares Outstanding	2,250,000	0
Preferred Stock, aggregate liquidation preference	$ 56,250	$ 0