Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 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	$ 4.5	$ 4.3	$ 13.8	$ 14.9
Capitalized real estate taxes	0.6	0.9	3.3	$ 2.9
Outstanding notes receivable	$ 19.9		$ 19.9		$ 13.2
Weighted average interest rate on outstanding notes receivable			4.10%	4.10%
Remaining commitment under notes receivable			$ 1.5
Interest Expense [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from deferred financing charges		0.4		$ 1.3
Depreciation and Amortization [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from deferred financing charges		$ 0.3		$ 0.9
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%