Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Common stock, shares outstanding	113,844,267	113,643,166
General partners' capital account, units outstanding	113,844,267	113,643,166
Limited partners' capital account, units outstanding	4,111,301
Preferred Stock, Liquidation Preference Per Share	$ 50.00
Limited Partner [Member]
Redeemable stock, shares/units issued and outstanding	98,371	103,504
General partners' capital account, units outstanding	113,844,267	113,643,166
Limited partners' capital account, units outstanding	4,111,301	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	113,844,267	113,643,166
Common stock, shares outstanding	113,844,267	113,643,166
Redeemable stock, shares/units issued and outstanding	98,371	103,504
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