Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
General Partner of Consolidated Operating Partnerships, Ownership Interest			1.00%
Capitalized interest	$ 4.7	$ 5.2	$ 9.3	$ 10.6
Capitalized real estate taxes	1.1	1.1	2.6	$ 2.1
Outstanding notes receivable	$ 19.1		$ 19.1		$ 13.2
Weighted average interest rate on outstanding notes receivable			4.10%	4.20%
Remaining commitment under notes receivable			$ 2.3
Interest Expense [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from deferred financing charges		0.4		$ 0.9
Depreciation and Amortization [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from deferred financing charges		$ 0.2		$ 0.5
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Outstanding common limited partnership units, ownership interest			92.00%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Outstanding common limited partnership units, ownership interest			94.00%