Subsequent Events/Other (Details) (USD $)	1 Months Ended	9 Months Ended		21 Months Ended
	Nov. 01, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Dec. 31, 2011	Mar. 31, 2011
Subsequent Events/Other (Textuals) [Abstract]
Land parcels acquired	1
Value Of Land Parcels Acquired Subsequent	$ 79,000,000
Number of Apartment Properties Sold Subsequent	2
Number of consolidated apartment units sold	542
Subsequent Event Sold Consolidated Property	50,400,000
Repayment of mortgage loans	24,000,000
Repayments of Notes Payable	222,100,000	253,858,000	575,641,000
Debt Instrument, Interest Rate, Stated Percentage	5.50%	6.625%		6.625%
Term Loan Principal Amount		500,000,000		500,000,000
Business Combination, Acquisition Related Costs		8,800,000	5,300,000
Noncash Project Abandonment Costs		6,141,000	4,052,000
Other Expenses		14,900,000	9,300,000
contracted aquisition price					1,325,000,000
contracted acquisition percent					26.50%
Remaining Percentage to be Contracted						26.50%
Remaining Acquisition Cost to be Contracted						1,580,000,000
BreakUpFee		150,000,000
Potential Business Combination Costs		1,900,000		6,300,000
Payments of Merger Related Costs, Financing Activities				2,600,000
Settlement Expense		4,200,000
Proceeds From Royalty Termination			4,500,000
Disposal Group Corporate Housing Business Sale			4,000,000
Seller Provided Financing			2,000,000
Proceeds Received From Seller Provided Finanacing		300,000		500,000
Discontinued Operation Corporate Housing Business Gain Loss On Disposal Of Discontinued Operation Net Of Tax				1,500,000
Estimates of lost revenue and garage reconstruction		22,800,000
Estimates Of Lost Revenue And Garage Reconstruction After Insurance Reimbursements		13,600,000
Initial insurance proceeds		3,500,000
Fees Related to Ownership Interest in Potential Transaction [Member]
Subsequent Events/Other (Textuals) [Abstract]
Potential Business Combination Costs				3,700,000
Lehman Fee [Member]
Subsequent Events/Other (Textuals) [Abstract]
BreakUpFee		70,000,000
BofA and Barclays Fee [Member]
Subsequent Events/Other (Textuals) [Abstract]
BreakUpFee	80,000,000
Term Loan [Member]
Subsequent Events/Other (Textuals) [Abstract]
Debt Instrument, Face Amount	$ 500,000,000