Mortgages and Notes Payable (Details) (USD $)	3 Months Ended	6 Months Ended			6 Months Ended		6 Months Ended		6 Months Ended					3 Months Ended		6 Months Ended		12 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended		6 Months Ended
	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010	Jan. 28, 2011	Jun. 30, 2011 Subsidiaries [Member] properties	Jan. 28, 2011 Maximum [Member]	Jun. 30, 2011 Line of Credit [Member]	Jan. 28, 2011 Line of Credit [Member]	Jun. 30, 2011 Secured Term Loan [Member]	Dec. 31, 2010 Secured Term Loan [Member]	Dec. 31, 2008 Secured Term Loan [Member]	Jun. 30, 2011 Secured Term Loan 1 [Member]	Jun. 30, 2011 Secured Term Loan 2 [Member]	Jun. 30, 2011 6.00% Convertible Guaranteed Note [Member]	Jun. 30, 2010 6.00% Convertible Guaranteed Note [Member]	Jun. 30, 2011 6.00% Convertible Guaranteed Note [Member]	Jun. 30, 2010 6.00% Convertible Guaranteed Note [Member]	Dec. 31, 2010 6.00% Convertible Guaranteed Note [Member]	Mar. 31, 2011 6.00% Convertible Guaranteed Note [Member]	Mar. 31, 2010 6.00% Convertible Guaranteed Note [Member]	Jun. 30, 2011 5.45% Exchangeable Guaranteed Note [Member]	Jun. 30, 2010 5.45% Exchangeable Guaranteed Note [Member]	Jun. 30, 2011 5.45% Exchangeable Guaranteed Note [Member]	Jun. 30, 2010 5.45% Exchangeable Guaranteed Note [Member]	Dec. 31, 2010 5.45% Exchangeable Guaranteed Note [Member]	Dec. 31, 2007 5.45% Exchangeable Guaranteed Note [Member]	Jun. 30, 2011 Other Debt Obligations [Member]	Jun. 30, 2010 Other Debt Obligations [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity								$ 300,000,000
Line of Credit Facility, Interest Rate Description		The new facility bears interest at 2.50% plus LIBOR if the Company's leverage ratio, as defined, is less than 50%, 2.85% plus LIBOR if the Company's leverage ratio is between 50% and 60% and 3.10% plus LIBOR if the Company's leverage ratio exceeds 60%.
Debt Instrument Interest Rate Stated Percentage Rate Range Minimum Excluding LIBOR				2.50%
Debt Instrument Interest Leverage Ratio Rate Range Minimum To Obtain Lower Interes tRate Stated Percentage				50.00%
Debt Instrument Interest Leverage Ratio Rate Range Maximum To Obtain Lower Interest Rate Stated Percentage				60.00%
Debt Instrument Interest Rate Stated Percentage Rate Range Middle Excluding LIBOR				2.85%
Debt Instrument Interest Rate Stated Percentage Rate Range Maximum Excluding LIBOR				3.10%
Debt Instrument Interest Leverage Ratio Rate						100.00%
Debt Instrument, Maturity Date							Jan. 31, 2014		Mar. 18, 2013							Jan. 31, 2030
Properties Pledged as Collateral					78
Line Of Credit Facility Increase Current Borrowing Capacity								225,000,000
Line of Credit Facility, Maximum Borrowing Capacity		300,000,000						525,000,000
Line of Credit Facility, Amount Outstanding							0
Letters of Credit Outstanding, Amount								4,109,000
Aggregate Financing Costs		3,941,000
Debt Instrument, Face Amount												25,000,000	35,551,000	115,000,000		115,000,000		115,000,000	115,000,000		62,150,000		62,150,000		62,150,000	450,000,000
Debt Instrument Interest Rate Stated Margin Percentage		0.60%
Derivative, Fixed Interest Rate									4.9196%
Derivative Liability, Fair Value, Gross Liability									4,503,000	5,280,000	5,696,000
Unamortized discount									1,693,000	2,183,000				(10,820,000)		(10,820,000)		(11,789,000)			(380,000)		(380,000)		(712,000)
Debt Instrument, Interest Rate, Stated Percentage																				6.00%						5.45%
Percent Of Notes Required To Be Repurchased At The Option Of The Holders On Set Dates	100.00%
Debt Instrument, Convertible, Conversion Ratio																141.1383
Debt Instrument, Description of Variable Rate Basis									LIBOR plus 60 basis points
Debt Instrument Convertible Principal Amount for Conversion														1,000		1,000
Debt Instrument, Convertible, Conversion Price														$ 7.09		$ 7.09
Exchangeable Note Exchange Price																										19.49
Debt Conversion, Original Debt, Amount																									25,500,000
Repurchase Of Exchangeable Notes		0	25,493,000																						25,493,000
Extinguishment of Debt, Gain (Loss), Net of Tax																									760,000		9,000	(2,000)
Writeoffs of Debt Discount And Deferred Financing Costs																									768,000
Carrying amount of debt component														104,180,000		104,180,000		103,211,000			61,770,000		61,770,000		61,438,000
Carrying amount of debt component														13,134,000		13,134,000		13,134,000			20,293,000		20,293,000		20,293,000
Effective interest rate														8.10%		8.10%		7.50%			7.00%		7.00%		7.00%
Period through which discount is being amortized, put date														Jan. 31, 2017		Jan. 31, 2017		Jan. 31, 2017			Jan. 31, 2012		Jan. 31, 2012		Jan. 31, 2012
Aggregate if-converted value in excess of aggregate principal amount																33,188,000		14,036,000					0		0
Coupon interest														1,725,000	1,725,000	3,450,000	2,958,000				847,000	847,000	1,694,000	1,820,000
Discount amortization														484,000	484,000	969,000	808,000				166,000	166,000	332,000	357,000
Interest Expense														$ 2,209,000	$ 2,209,000	$ 4,419,000	$ 3,766,000				$ 1,013,000	$ 1,013,000	$ 2,026,000	$ 2,177,000