Commitments And Contingencies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 property	Dec. 31, 2013	Dec. 31, 2012
Long-term Purchase Commitment [Line Items]
Ground leases, expiration date	Jun. 30, 2069
Operating leases, rental expense	$ 5,300,000	$ 5,600,000	$ 5,700,000
Number of real estate properties	2
Capital leases, total assets	16,800,000	16,800,000
Capital leases, accumulated depreciation	13,000,000	12,200,000
Capital leases, future minimum payments	37,840,000
Capital leases, future minimum payments, interest	16,800,000
Capital leases, future minimum payments, present value of net minimum payments	21,000,000
Shares issued in exchange of interests	0	0
Notes receivable from real estate joint ventures and partnerships		16,100,000
Receipt of cash and real property		19,100,000
Increase in noncontrolling interest	(11,015,000)	16,177,000	(394,000)
Total assets	3,814,094,000	4,223,929,000
Minimum [Member]
Long-term Purchase Commitment [Line Items]
Operating leases, term range, in years	1 year
Maximum [Member]
Long-term Purchase Commitment [Line Items]
Operating leases, term range, in years	25 years
DownREIT [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures	3	3
Shares issued in exchange of interests	0	0
Aggregate redemption value	52,000,000	41,000,000
Consolidated Entities [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures		2
Unconsolidated [Member]
Long-term Purchase Commitment [Line Items]
Number of real estate joint ventures		2
Sheridan, Colorado [Member]
Long-term Purchase Commitment [Line Items]
Total assets		23,200,000
Capital Additions [Member]
Long-term Purchase Commitment [Line Items]
Purchase contract, commitment	64,300,000
Capital Additions [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Purchase contract, period (in months)	12 months
Capital Additions [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Purchase contract, period (in months)	36 months
Development Addition [Member]
Long-term Purchase Commitment [Line Items]
Purchase contract, commitment	23,800,000
Purchase contract, date	Aug. 01, 2016
Future investment amount	$ 29,100,000