Mortgages and Notes Payable (Details) (USD $)	12 Months Ended							0 Months Ended				12 Months Ended							12 Months Ended				12 Months Ended					12 Months Ended		0 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2012 Maximum [Member]	Feb. 12, 2013 Unsecured Revolving Credit Facility [Member] Minimum [Member]	Feb. 12, 2013 Unsecured Revolving Credit Facility [Member] Maximum [Member]	Dec. 31, 2013 Mortgages and Notes Payable [Member]	Dec. 31, 2013 Line of Credit [Member]	Dec. 31, 2013 Unsecured Term Loan [Member] Minimum [Member]	Dec. 31, 2013 Unsecured Term Loan [Member] Maximum [Member]	Dec. 31, 2013 Interest Rate Swap [Member]	Dec. 31, 2012 Interest Rate Swap [Member]	Dec. 31, 2013 Secured Term Loan [Member]	Dec. 31, 2012 Secured Term Loan [Member]	Dec. 31, 2013 Secured Term Loan 1 [Member]	Dec. 31, 2013 Secured Term Loan 2 [Member]	Dec. 31, 2012 Condition One [Member] Secured Term Loan [Member]	Dec. 31, 2012 Condition Four [Member] Secured Term Loan [Member]	Dec. 31, 2013 Unsecured Revolving Credit Facility, Expiring February 2018 [Member]	Dec. 31, 2013 Unsecured Revolving Credit Facility, Expiring February 2018 [Member] Minimum [Member]	Dec. 31, 2013 Unsecured Revolving Credit Facility, Expiring February 2018 [Member] Maximum [Member]	Dec. 31, 2013 Unsecured Revolving Credit Facility, Expiring February 2018 [Member] Unsecured Revolving Credit Facility [Member]	Feb. 12, 2013 Unsecured Revolving Credit Facility, Expiring February 2018 [Member] Unsecured Revolving Credit Facility [Member]	Dec. 31, 2013 Term Loan Facility from Key Bank [Member]	Dec. 31, 2013 Term Loan Facility from Key Bank [Member] Minimum [Member]	Dec. 31, 2013 Term Loan Facility from Key Bank [Member] Maximum [Member]	Feb. 12, 2013 Term Loan Facility from Key Bank [Member] Unsecured Term Loan [Member]	Feb. 12, 2013 Secured Revolving Credit Facility, Expiring January 2015 [Member] Secured Revolving Credit Facility [Member]	Dec. 31, 2012 Secured Revolving Credit Facility, Expiring January 2015 [Member] Secured Term Loan [Member]	Dec. 31, 2013 Unsecured Revolving Credit Facility, Expiring January 2019 [Member]	Dec. 31, 2012 Unsecured Revolving Credit Facility, Expiring January 2019 [Member] Secured Term Loan [Member] Minimum [Member]	Dec. 31, 2012 Unsecured Revolving Credit Facility, Expiring January 2019 [Member] Secured Term Loan [Member] Maximum [Member]
Debt Instrument [Line Items]
Mortgages and notes payable	$ 1,197,489,000	$ 1,415,961,000
Effective interest rate				3.60%	3.60%	8.50%	8.50%
Weighted-average interest rate	5.30%	5.60%												1.05%	1.42%
Debt Instrument, Term																														5 years
Interest rate stated percentage rate range minimum excluding LIBOR								1.50%	2.05%			1.45%	2.00%							2.00%	2.85%		0.95%	1.725%				1.10%	2.10%					1.50%	2.25%
Debt Instrument, Basis Spread on Variable at the End of the Period																						1.15%					1.35%						1.75%
Line of Credit Facility, Remaining Borrowing Capacity	344,356,000
Outstanding letters of credit	7,644,000
Debt instrument amount																151,000,000	255,000,000	25,000,000	35,551,000						400,000,000	300,000,000				250,000,000	300,000,000	255,000,000
Revolving credit facility amount outstanding											48,000,000
Gains (charges) on debt satisfaction from continuing operations	(11,861,000)	(16,000)	45,000																1,578,000
Interest Paid, Capitalized	2,397,000	3,062,000	1,792,000
Scheduled Principal and Balloon Payments on Mortgages and Notes Payable
2014										123,212,000
2015										301,591,000
2016										168,899,000
2017										137,035,000
2018										188,764,000
Thereafter										731,988,000
Long-term debt										$ 1,651,489,000