Stockholders' Equity (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended				6 Months Ended	3 Months Ended		6 Months Ended				6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Series F Preferred Stock [Member]	Jun. 30, 2012 Series F Cumulative Preferred Stock [Member]	Jun. 30, 2012 Convertible Common Stock [Member]	Jun. 30, 2012 Restricted Stock Unit Awards [Member]	Jun. 30, 2011 Restricted Stock Unit Awards [Member]	Jun. 30, 2012 Restricted Stock Unit Awards [Member]	Jun. 30, 2011 Restricted Stock Unit Awards [Member]	Jun. 30, 2012 ATM [Member]	Mar. 01, 2012 ATM [Member] Maximum [Member]	Jun. 30, 2012 ATM [Member] Common Stock [Member]	Mar. 01, 2012 ATM [Member] Common Stock [Member]
Stockholders' Equity (Textual) [Abstract]
Shares of common stock issuable under the At-the-Market offering											12,500,000
Aggregate gross sale proceeds of common stock under the At-the Market offering													$ 125,000
Issuance of common stock under the At-the-Market offering										1,532,598
Weighted average price of common stock issued under the At-the-Market offering										$ 12.03
Net proceeds from issuance of common stock under the At-the-Market offering										18,063
Sales agent commission												369
Converted Shares of common stock					280,991
Conversion of Units to Common Stock					2,469
Restricted stock/unit awards to employees								365,137	292,339
Fair value of restricted stock/unit awards								4,327	3,248
Vesting period of restricted stock/unit awards to employees								3 years
Recognized compensation expense related to restricted stock/unit awards						1,299	1,081	2,398	1,726
Unrecognized compensation expense related to restricted stock/unit awards						$ 6,890		$ 6,890
Weighted average period during which unrecognized compensation expense is expected to be recognized								11 months 19 days
Minimum fixed coupon rate of preferred stock				2.375%
Number of years of U.S treasury rate one			30 years
Number of years of U.S treasury rate two			10 years
New coupon rate of preferred stock			5.705%	5.705%
LIBOR rate			3 month LIBOR