Investments in Unconsolidated Entities (Details Textuals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Unamortized investment in joint venture primarily attributable to appreciation of underlying properties and transaction cost	$ 110,063
Sunrise [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of partnership owned	24.00%
New ownership including new acquisitions	34.00%
Management fee to Sunrise	$ 37,573	$ 37,751	$ 36,403
Sunrise [Member] | Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Additional optional renewal periods	5 years
Sunrise [Member] | Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Additional optional renewal periods	15 years
Agreement term expiration date	Dec. 31, 2032