Supplemental Information to Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flow information
Interest paid, net of capitalized interest	$ 100,375	$ 105,276	$ 115,990
Capitalized Interest	437		281
Income Taxes Paid (Refunded)	1,876	3,663	(54,173)
Supplemental schedule of noncash investing and financing activities:
Dividends Declared Not Paid	4,763	452	452
Exchange of units for common stock
Conversion of Units to Common Stock	0	0	0
Property Transfer to Lender in Satisfaction of Non-Recourse Mortgage Loan:
Net Investment of Real Estate	(3,200)
Prepaid Expenses and Other Assets, Net	(1,987)
Mortgage Loan Payable, Net	5,040
Loss from Retirement of Debt	(147)
In conjunction with property and land acquisitions, the following liabilities were assumed
Mortgage loan payable assumed in conjunction with a property acquisition	(24,417)
Notes receivable issued in conjunction with certain property sales	7,029	168	20,645
Write-off of fully depreciated assets	(58,357)	(59,485)	(55,089)
Noncontrolling Interest [Member]
Exchange of units for common stock
Conversion of Units to Common Stock	(1,109)	(316)	(7,817)
Common Stock [Member]
Exchange of units for common stock
Conversion of Units to Common Stock	1	1	4
Additional Paid-in Capital [Member]
Exchange of units for common stock
Conversion of Units to Common Stock	$ 1,108	$ 315	$ 7,813