Fair Value Measurements (Quantitative Information About Significant Unobservable Inputs (Level 3) Used) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Fixed-Rate Debt [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	1.20%		1.10%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Fixed-Rate Debt [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	7.20%		6.50%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Variable-Rate Debt [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	0.80%		1.40%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Variable-Rate Debt [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	5.00%		5.00%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Notes Receivable From Real Estate Joint Ventures And Partnerships [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	2.70%		3.00%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Tax Increment Revenue Bonds [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate	7.50%		7.50%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Tax Increment Revenue Bonds [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Expected Future Inflation Rate	1.00%		1.00%
Fair Value Input, Expected Future Growth Rate	1.00%		1.00%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Tax Increment Revenue Bonds [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Expected Future Inflation Rate	2.00%		2.00%
Fair Value Input, Expected Future Growth Rate	2.00%		4.00%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Impaired Property [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Discount Rate			10.00%
Fair Value Input, Holding Period (Years)			1 year
Fair Value Input, Expected Future Inflation Rate			3.00%	[1]
Fair Value Input, Market Rent Growth Rate			3.00%	[1]
Fair Value Input, Expense Growth Rate			3.00%	[1]
Fair Value Input, Vacancy Rate			5.00%	[1]
Fair Value Input, Renewal Rate			75.00%	[1]
Fair Value Input, Market Rent Rate			$ 10.52	[1]
Fair Value Input, Leasing Costs Per Square Foot			16.50	[1]
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Impaired Property [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Market Capitalization Rate			9.30%
Significant Unobservable Inputs (Level 3) [Member] | Discounted Cash Flows [Member] | Impaired Property [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Input, Market Capitalization Rate			9.50%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Property [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Property	11,876,000	[2]	19,679,000	[3]
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Impaired Property [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Property	8,576,000	[2]	13,906,000	[3]
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notes receivable from real estate joint ventures and partnerships	85,897,000		93,572,000
Tax increment revenue bonds	25,850,000		26,505,000
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed-Rate Debt [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Debt	2,055,495,000		2,094,122,000
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member] | Variable-Rate Debt [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Debt	$ 289,560,000		$ 223,759,000

[1] Only applies to one property valuation.

[2] In accordance with our policy of evaluating and recording impairments on the disposal of long-lived assets, property with a carrying amount of $14.3 million was written down to a fair value of $11.9 million, resulting in a loss of $2.4 million, which was included in earnings for the period. Management’s estimate of the fair value of these properties was determined using bona fide purchase offer for the Level 2 inputs. See the quantitative information about the significant unobservable inputs used for our Level 3 fair value measurements table below.

[3] In accordance with our policy of evaluating and recording impairments on the disposal of long-lived assets, property with a carrying amount of $22.4 million was written down to a fair value of $19.7 million less costs to sell of $.3 million, resulting in a loss of $3.0 million, which was included in earnings for the period. Management’s estimate of fair value of these properties was determined using a bona fide purchase offer for the Level 2 inputs. See the quantitative information about the significant unobservable inputs used for our Level 3 fair value measurements table below.