Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 months years	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Line Items]
Interest capitalized costs	$ 5,255,000	$ 9,384,000	$ 8,900,000
Associated costs capitalized	3,028,000	3,007,000	2,896,000
UPREIT share Units	565,509	528,004	1,086,612
Exchange of UPREIT Units for common shares	0	0	0
Depreciation expense from continuing operations	143,272,000	125,634,000	117,694,000
Depreciation expense from discontinued operations	0	832,000	2,346,000
Federal Deposit Insurance Corporation limit	250,000
Allowance for accounts due (in days)	60
Allowance for doubtful receivables	2,869,000	3,134,000
Accumulated amortization of deferred charges	8,231,000	10,788,000
Other intangible assets	12,518,000	10,093,000
Minimum estimated useful lives of intangible assets (in months)	6
Maximum estimated useful lives of intangible assets (in years)	3
Accumulated amortization of intangible assets	10,194,000	8,680,000
Amortization expense continuing operations	1,547,000	1,034,000	878,000
Amortization expense discontinued operations	0	7,000	10,000
Fair value debt amount	2,826,006,000	2,678,524,000
Carrying value debt amount	2,663,336,000	2,618,932,000
Residential apartment units lease terms	one year or less
Percentage of other expenses to total purchase price	0.64%	0.85%
Advertising expense from continuing operation	4,856,000	4,604,000	4,321,000
Advertising expense from discontinuing operation	0	2,000	116,000
Federal income tax basis difference	420,930,000	478,591,000
Excess taxable income percentage	100.00%	100.00%	100.00%
Deferred tax assets	13,185,000	12,750,000
Deferred tax assets from sale of variable interest entity		2,555,000
Reserve against deferred tax assets	13,185,000	12,750,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization terms of deferred charges (in months & years)	10
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization terms of deferred charges (in months & years)	3
REIT taxable income to shareholders	90.00%
Noncontrolling Interest [Member]
Summary Of Significant Accounting Policies [Line Items]
Exchange of UPREIT Units for common shares	$ 11,399,000	$ 10,234,000	$ 21,332,000