SHARE INCENTIVE PLAN Share Incentive Plan (Details) (USD $)	12 Months Ended					12 Months Ended	0 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Trustee [Member]	Mar. 15, 2012 Officer [Member]	Dec. 31, 2012 2006 Plan [Member]	Mar. 15, 2012 LTIP Units [Member] Officer [Member]	May 10, 2012 Restricted Stock [Member] Trustee [Member]	Mar. 15, 2012 Restricted Stock [Member] Officer [Member]	Mar. 15, 2012 Restricted Stock [Member] Other Employees [Member]	Dec. 31, 2009 Long Term Investment Alignment Program [Member] Senior Executives [Member]	Dec. 31, 2012 Long Term Investment Alignment Program [Member] Senior Executives [Member]	Dec. 31, 2012 LTIP Units and Restricted Stock [Member]	Dec. 31, 2011 LTIP Units and Restricted Stock [Member]	Dec. 31, 2010 LTIP Units and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Increase in Number of Shares Authorized						1,900,000
Maximum Equivalent Value of Common Shares a Participant Can be Awarded						2,100,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures							279,611	19,360	1,358	9,435
Percent of Awards Issued to Officers Subject to Performance Measures					17.00%
Total Value of Restricted Shares and LTIP Units as of the Grant Date													$ 6,400,000
Share compensation expense	4,021,000	4,299,000	4,104,000											2,600,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	9,600,000												3,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value													$ 21.98	$ 19.08	$ 16.73
Long Term Incentive and Share Based Compensation Expense													3,600,000	4,000,000	3,800,000
Shares Granted to Trustees for Trustee Fees Vesting on One Year Anniversary of Grant Date								8,983
Shares Granted to Trustees for Trustee Fees Begin Vesting on Two Year Anniversary of Grant Date								10,377
Annual Vesting Rate of Shares Granted to Trustees That Begin Vesting on the Second Anniversary of Grant Date								33.00%
Trustee Fees	$ 0.2
Max Percentage of Future Fund III Promote That May be Awarded to Senior Executives											25.00%
Percent of Units Awarded												81.00%
Options Outstanding and Vested to Officers and Employees	100,647
Options Outstanding and Vested to Non Employee Turstees				37,000