Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
Preferred Stock, Par or Stated Value Per Share (usd per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	9,945,539	9,765,900
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share (usd per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	200,000,000	200,000,000
Common Stock, Shares, Issued	84,276,055	83,879,779
Common Stock, Shares, Outstanding	84,276,055	83,879,779
6.75% Series C Cumulative Redeemable Perpetual Preferred Stock
Preferred Stock, Par or Stated Value Per Share (usd per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	54,461	54,461
Preferred Stock, Shares Issued	54,458	54,458
Preferred Stock, Shares Outstanding	54,458	54,458
Cumulative Series D 6% Non-Qualified Preferred Stock
Preferred Stock, Par or Stated Value Per Share (usd per share)	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	0	179,639
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0