Investments in Joint Ventures (Narrative) (Details)		3 Months Ended			9 Months Ended
		Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Property operating and maintenance		$ 60,090,000		$ 53,679,000	$ 164,188,000		$ 156,804,000
Equity method investment ownership percentage		20.00%			20.00%
Equity in income of joint ventures	[1]	$ 1,255,000	[2]	1,866,000	$ 4,857,000	[2]	5,052,000
Number of joint ventures accounted for under equity method investments					3
Maximum guaranteed amount of loans utilized for construction and development activities for joint ventures		0			$ 0
Fees earned for property and asset management, construction, development, and other services to joint ventures		$ 1,400,000		$ 1,400,000	$ 4,000,000		$ 4,000,000
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		31.30%			31.30%
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage		20.00%			20.00%
Hurricane [Member]
Schedule of Equity Method Investments [Line Items]
Equity in income of joint ventures	[1],[2]	$ 400,000			$ 400,000
Non-consolidated entity [Member] | Hurricane [Member]
Schedule of Equity Method Investments [Line Items]
Property operating and maintenance		$ 1,300,000			$ 1,300,000

[1] Equity in income excludes our ownership interest of fee income from various services provided by us to the Funds.

[2] Equity in income for the three and nine months ended September 30, 2017 includes our ownership interest of the hurricane related expenses of approximately $0.4 million.