Discontinued Operations Discontinued Operations (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Real Estate									$ 66,000,000	$ 34,900,000	$ 73,000,000
Payments to Acquire Notes Receivable											20,400,000
Proceeds from Collection of Notes Receivable											8,900,000
Revenues included in Discontinued Operations	125,322,000	124,275,000	125,923,000	124,897,000	117,584,000	119,217,000	117,523,000	121,837,000
Discontinued Operation, Tax Effect of Discontinued Operation									(289,000)	(166,000)	(2,085,000)
Wholly Owned Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership Interest									100.00%		100.00%
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues included in Discontinued Operations									$ 7,700,000	$ 11,400,000	$ 19,300,000