Equity, Capital and Other Interests - Issued and Outstanding Preferred Shares and Preference Units (Parenthetical) (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	100,000,000	100,000,000
Preferred Stock
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	$ 50	$ 50
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%
Preferred Stock | 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	$ 50	$ 50
Preferred Stock Preference Units Dividend Rate Percentage	8.29%	8.29%