Disclosure About Fair Value of Financial Instruments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Assets [Abstract]
Marketable securities of non-qualified deferred compensation plan (in prepaid expenses and other assets)	$ 3,876,000		$ 3,876,000		$ 3,479,000
Tax increment financing bond (in prepaid expenses and other assets)	15,228,000		15,228,000		15,699,000
Total Assets	19,104,000		19,104,000		19,178,000
Noncontrolling Interests in the Operating Partnership	125,075,000		125,075,000		120,838,000
Liability [Abstract]
Non-qualified deferred compensation obligation (in accounts payable, accrued expenses and other liabilities)	3,876,000		3,876,000		4,091,000
Tax increment financing bond [Abstract]
Unrealized gain/(loss) (in AOCL)	(336,000)	(73,000)	(471,000)	146,000
Amount by which outstanding principal amount exceeds estimated fair value	3,013,000		3,013,000		2,543,000
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgages and notes receivable	18,809,000		18,809,000		19,044,000
Mortgages and notes payable	1,615,068,000		1,615,068,000		1,522,945,000
Financing obligations	32,869,000		32,869,000		33,114,000
Level 1 [Member]
Assets [Abstract]
Marketable securities of non-qualified deferred compensation plan (in prepaid expenses and other assets)	3,876,000		3,876,000		3,479,000
Tax increment financing bond (in prepaid expenses and other assets)	0		0		0
Total Assets	3,876,000		3,876,000		3,479,000
Noncontrolling Interests in the Operating Partnership	125,075,000		125,075,000		120,838,000
Liability [Abstract]
Non-qualified deferred compensation obligation (in accounts payable, accrued expenses and other liabilities)	3,876,000		3,876,000		4,091,000
Level 3 [Member]
Assets [Abstract]
Marketable securities of non-qualified deferred compensation plan (in prepaid expenses and other assets)	0		0		0
Tax increment financing bond (in prepaid expenses and other assets)	15,228,000		15,228,000		15,699,000
Total Assets	15,228,000		15,228,000		15,699,000
Noncontrolling Interests in the Operating Partnership	0		0		0
Liability [Abstract]
Non-qualified deferred compensation obligation (in accounts payable, accrued expenses and other liabilities)	0		0		0
Tax Increment Financing Bond [Member]
Tax increment financing bond [Abstract]
Beginning balance	15,564,000	17,090,000	15,699,000	16,871,000
Unrealized gain/(loss) (in AOCL)	(336,000)	(73,000)	(471,000)	146,000
Ending balance	15,228,000	17,017,000	15,228,000	17,017,000
Amount by which outstanding principal amount exceeds estimated fair value	3,000,000		3,000,000
Maturity date			Dec. 01, 2020
Decrease in fair value of bond if yield-to-maturity was 100 basis points higher	600,000		600,000
Increase in fair value of bond if yield-to-maturity was 100 basis points lower	600,000		600,000
Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgages and notes receivable	19,141,000		19,141,000		19,093,000
Mortgages and notes payable	1,725,186,000		1,725,186,000		1,581,518,000
Financing obligations	20,852,000		20,852,000		23,880,000
Carrying value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgages and notes receivable	18,809,000		18,809,000		19,044,000
Mortgages and notes payable	1,615,068,000		1,615,068,000		1,522,945,000
Financing obligations	$ 32,869,000		$ 32,869,000		$ 33,114,000