Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Common stock, shares outstanding	113,808,292
General Partners' Capital Account, Units Outstanding	113,808,292
Limited Partners' Capital Account, Units Outstanding	4,135,668
Preferred Stock, Liquidation Preference Per Share	$ 50.00
Limited Partner [Member]
General Partners' Capital Account, Units Outstanding	113,808,292	113,643,166
Limited Partners' Capital Account, Units Outstanding	4,135,668	4,191,586
Preferred Units, Issued	867,846	867,846
Preferred Units, Outstanding	867,846	867,846
Parent Company [Member]
Common stock, par value per share	$ 0.01	$ 0.01
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	113,808,292	113,643,166
Common stock, shares outstanding	113,808,292	113,643,166
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Preferred Stock, Shares Issued	867,846	867,846
Preferred Stock, Shares Outstanding	867,846	867,846
Preferred Stock, Liquidation Preference Per Share	$ 50	$ 50