Summary of Significant Accounting Policies (Details Textuals 1) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2009	Dec. 31, 2008	Jun. 02, 2010
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Prior period depreciation and Amortization adjustment		$ 4.7
Development expense for land	7.7				7.7
Revenue increased by straight-line rent adjustment	4.9			3.1	13.2	7.0
Increased revenue due to amortization of deferred rent	0.6			0.6	1.7	2.2
Decrease in revenue due to amortization of lease incentives	0.4			0.2	1.0	1.2
Increase in Common shares available for future awards									6,000,000
Increase in shares due to amendments in plan, shares solely available for options and share appreciation rights									3,600,000
Common shares available for future awards	5,788,395				5,788,395
Common shares available for options and stock appreciation rights	4,578,737				4,578,737
Options awarded, term					one to ten-year
Stock-based compensation expense	1.6			1.7	4.9	4.8
Stock-based compensation expense, capitalized	0.4			0.4	1.1	1.0
Additional income related to electricity charges			0.5
Overstatement of revenue due to under billing			0.5
Understatement of Revenue							0.3	0.2
Distributable income minimum percentage					90.00%
Outstanding purchase money mortgage	$ 7.2				$ 7.2
Purchase money mortgage loan repayments terms					start in 2012, to be fully paid in 2014