Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 segment sqft foreign	Dec. 31, 2012 Retirement Plan [Member]	Dec. 31, 2012 Retirement Plan [Member] Minimum [Member]	Dec. 31, 2010 Retirement Plan [Member] Minimum [Member]	Dec. 31, 2012 Retirement Plan [Member] Maximum [Member]	Dec. 31, 2012 Supplemental Retirement Plans [Member] plans	Dec. 31, 2011 Supplemental Retirement Plans [Member]	Dec. 31, 2011 Supplemental Retirement Plans [Member] Minimum [Member]	Dec. 31, 2011 Supplemental Retirement Plans [Member] Maximum [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] Minimum [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] Maximum [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] New Balance Annual Addtions [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] New Balance Annual Addtions [Member] Minimum [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] New Balance Annual Addtions [Member] Maximum [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plan, Defined Contribution Plan [Member] Old Balance Annual Addtions [Member]	Dec. 31, 2012 Savings and Investment Plan, Defined Contribution Plan [Member]	Dec. 31, 2012 Restricted Shares [Member]	Dec. 31, 2011 Restricted Shares [Member] Officer [Member]	Dec. 31, 2011 Share Options [Member]	Dec. 31, 2011 Share Options [Member] Non-Officer [Member]	Dec. 31, 2011 Share Options [Member] Officer [Member]	Dec. 31, 2012 Service Based Awards [Member] Restricted Shares [Member]	Dec. 31, 2012 Market Based Awards [Member] Restricted Shares [Member]	Dec. 31, 2012 Market Based Awards [Member] Market Based Awards Relative To FTSE NAREIT United States Shopping Center Index [Member]	Dec. 31, 2012 Market Based Awards [Member] Market Based Awards Relative To Three Year Absolute Total Shareholder Return [Member]	Dec. 31, 2012 Building [Member]	Dec. 31, 2012 Building [Member] Minimum [Member]	Dec. 31, 2012 Building [Member] Maximum [Member]	Dec. 31, 2012 Parking Lot Surfacing And Equipment [Member] Minimum [Member]	Dec. 31, 2012 Parking Lot Surfacing And Equipment [Member] Maximum [Member]	Dec. 31, 2012 Tenant Base [Member]	Dec. 31, 2012 Houston, Texas Geographic Concentration [Member]	Dec. 31, 2012 Other Parts of Texas Geographic Concentration [Member]	Dec. 31, 2012 Revenues, Segment [Member]	Dec. 31, 2012 Net Operating Income, Segment [Member]	Dec. 31, 2012 Assets, Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Date of establishment	1948
Square footage of operating properties	53,700,000
Concentrations of risk																															3.20%	21.10%	7.70%	10.00%	10.00%	10.00%
Estimated useful lives																										40 years	18 years	40 years	10 years	20 years
Depreciation method, New Development	no depreciation is recorded on these assets until rent commences or no later than one year from the completion of major construction
Capitalization method, New Development	The capitalization of such costs ceases at the earlier of one year from the completion of major construction or when the property, or any completed portion, becomes available for occupancy.
Single purpose entity, ownership percentage	100.00%
Dividend distribution tax payment description	As long as we distribute at least 90% of the taxable income of the REIT (without regard to capital gains or the dividends paid deduction) to our shareholders as dividends, we will not be taxed on the portion of our income we distribute as dividends unless we have ineligible transactions.
Share award price determination method																	restricted shares for officers and trust managers are granted at no purchase price		The grant price for our options is calculated as an average of the high and low of the quoted fair value of our common shares on the date of grant.
Vesting period (years) for share options and awards																	3 years	5 years		3 years	5 years	3 years	3 years
Percentage allocation of market based awards																								50.00%	50.00%
Option fair value assumptions and methods																			The fair value of share options was estimated on the date of grant using the Black-Scholes option pricing method based on certain expected weighted average assumptions; including the dividend yield, the expected volatility, the expected life and the risk free interest rate.
Maximum term of option award (years)																			10 years
Period of historical data used to estimate volatility (years)																			10 years
Service credit percentage			3.00%		5.00%								3.00%	5.00%
Interest credit rate		4.50%		2.05%			7.50%					4.50%			7.50%
Vesting period (years)		3 years						5 years	10 years
Number of retirement plans						2
Interest credit rate, inactive															December 31 90-day LIBOR rate plus .50%
Defined contribution plan, vesting period										5 years	10 years					5 years
Defined contribution plan, minimum annual contribution per employee, percent																1.00%
Defined contribution plan, maximum employee contribution, description																established annually by the IRS
Defined contribution plan, employer matched rate of employee contributions, amount																$ 0.50
Defined contribution plan, employer matching contribution, percent																6.00%
Number of foreign operations	0
Number of reportable segments	1