Fair Value Measurements (Quantitative Information About Significant Unobservable Inputs (Level 3) Used) (Details) (USD $)															12 Months Ended
	Dec. 31, 2012 Impaired Property [Member]		Dec. 31, 2011 Impaired Property [Member]		Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Fixed Rate Debt [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Fixed Rate Debt [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Variable Rate Debt [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Variable Rate Debt [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Impaired Property [Member]		Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Impaired Property [Member]		Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Impaired Property [Member] Minimum [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Impaired Property [Member] Maximum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Fixed Rate Debt [Member] Minimum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Fixed Rate Debt [Member] Maximum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Variable Rate Debt [Member] Minimum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Variable Rate Debt [Member] Maximum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Notes Receivable From Real Estate Joint Ventures And Partnerships [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Tax Increment Revenue Bonds [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Tax Increment Revenue Bonds [Member] Minimum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Tax Increment Revenue Bonds [Member] Maximum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Impaired Property [Member]		Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Impaired Property [Member] Minimum [Member]	Dec. 31, 2012 Significant Unobservable Inputs (Level 3) [Member] Discounted Cash Flows [Member] Impaired Property [Member] Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Property	$ 19,679,000	[1]	$ 98,596,000	[2]							$ 13,906,000	[1]	$ 98,207,000	[2]
Notes receivable from real estate joint ventures and partnerships					93,572,000	153,532,000
Debt							2,094,122,000	2,054,670,000	223,759,000	531,353,000
Tax increment revenue bonds					26,505,000	26,505,000
Fair Value Input Discount Rate															8.00%	13.00%	1.10%	6.50%	1.40%	5.00%	3.00%	7.50%			10.00%
Fair Value Input Market Capitalization Rate																											9.30%	9.50%
Fair Value Input Holding Period (Years)																									1 year
Fair Value Input Expected Future Inflation Rate																							1.00%	2.00%	3.00%	[3]
Fair Value Input Market Rent Growth Rate																									3.00%	[3]
Fair Value Inputs Expense Growth Rate																									3.00%	[3]
Fair Value Inputs Vacancy Rate																									5.00%	[3]
Fair Value Input Renewal Rate																									75.00%	[3]
Fair Value Inputs Market Rent Rate																									10.52	[3]
Fair Value Inputs Leasing Costs Per Square Foot																									$ 16.50	[3]
Fair Value Inputs Expected Future Growth Rate																							1.00%	4.00%

[1] 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 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.

[2] In accordance with our policy of evaluating and recording impairments on the disposal of long-lived assets, property with a carrying amount of $135.5 million was written down to a fair value of $98.6 million, resulting in a loss of $36.9 million, which was included in earnings for the period. Management’s estimate of the fair value of these properties was determined using the expected sales price of an executed agreement for the Level 2 input and using third party broker valuations, bona fide purchase offers, cash flow models and discount rates ranging from 8% to 13% for the Level 3 inputs.

[3] Only applies to one property valuation.