Equity, Capital and Other Interests Preferred (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Class of Stock [Line Items]
Preferred Shares of beneficial interest, $0.01 par value; 100,000,000 shares authorized; 803,600 shares issued and outstanding as of September 30, 2015 and 1,000,000 shares issued and outstanding as of December 31, 2014	$ 40,180		$ 40,180		$ 50,000
Partial redemption of 8.29% Series K Cumulative Redeemable			(9,820)	$ 0
Premium on redemption of Preference Units	0	$ 0	(2,789)	0
ERPOP [Member]
Class of Stock [Line Items]
Partial redemption of 8.29% Series K Cumulative Redeemable			(9,820)	0
Premium on redemption of Preference Units	0	$ 0	2,789	$ 0
Preference Units	$ 40,180		$ 40,180		$ 50,000
Series K Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock Preference Units Issued	803,600		803,600		1,000,000
Preferred Stock Preference Units Outstanding	803,600		803,600		1,000,000
Preferred Stock Preference Units Redemption Price Per Share Unit	$ 50.00		$ 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; 803,600 shares issued and outstanding as of September 30, 2015 and 1,000,000 shares issued and outstanding as of December 31, 2014	$ 40,180		$ 40,180		$ 50,000
Preferred Stock Preference Units Repurchased and Retired			196,400
Partial redemption of 8.29% Series K Cumulative Redeemable			$ 9,820
Treasury Stock Retired, Cash Consideration			12,700
Premium on redemption of Preference Units			$ 2,789
Series K Preferred Stock [Member] | ERPOP [Member]
Class of Stock [Line Items]
Preferred Stock Preference Units Issued	803,600		803,600		1,000,000
Preferred Stock Preference Units Outstanding	803,600		803,600		1,000,000
Preferred Stock Preference Units Redemption Price Per Share Unit	$ 50.00		$ 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
Preference Units	$ 40,180		$ 40,180		$ 50,000