Equity, Capital and Other Interests Preferred (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	100,000,000	100,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Shares of beneficial interest, $0.01 par value; 100,000,000 shares authorized; 745,600 shares issued and outstanding as of March 31, 2016 and December 31, 2015	$ 37,280	$ 37,280
ERPOP [Member]
Class of Stock [Line Items]
8.29% Series K Cumulative Redeemable Preference Units; liquidation value $50 per unit; 745,600 units issued and outstanding at March 31, 2016 and December 31, 2015	$ 37,280	$ 37,280
Series K Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock Preference Units Issued	745,600	745,600
Preferred Stock Preference Units Outstanding	745,600	745,600
Preferred Stock Preference Units Redemption Price Per Share Unit	$ 50.00	$ 50.00
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%
Preferred Stocks Preference Units Redemption Date	Dec. 10, 2026
Annual Dividend Per Preferred Share Preference Unit	$ 4.145
Preferred Shares of beneficial interest, $0.01 par value; 100,000,000 shares authorized; 745,600 shares issued and outstanding as of March 31, 2016 and December 31, 2015	$ 37,280	$ 37,280
Series K Preferred Stock [Member] | ERPOP [Member]
Class of Stock [Line Items]
Preferred Stock Preference Units Issued	745,600	745,600
Preferred Stock Preference Units Outstanding	745,600	745,600
Preferred Stock Preference Units Redemption Price Per Share Unit	$ 50.00	$ 50.00
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%
Preferred Stocks Preference Units Redemption Date	Dec. 10, 2026
Annual Dividend Per Preferred Share Preference Unit	$ 4.145
8.29% Series K Cumulative Redeemable Preference Units; liquidation value $50 per unit; 745,600 units issued and outstanding at March 31, 2016 and December 31, 2015	$ 37,280	$ 37,280