Summary Of Significant Accounting Policies (Narrative) (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) ft² plan item customer segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Significant Accounting Policies [Line Items]
Square footage of operating properties (in square feet) | ft²	30.2
Accrued Rent, Accrued Contract Receivables and Accounts Receivable, net	$ 81,016	$ 83,639
Allowance for credit loss	$ 0
Real estate asset, estimated useful life	40 years
Allowance for doubtful accounts			$ 6,900
Charge to bad debt			2,400
Deductions from allowance for doubtful accounts			3,000
Number of reportable segments | segment	1
Other	$ 11,578	$ 14,179	$ 13,311
Geographic Distribution, Foreign [Member]
Significant Accounting Policies [Line Items]
Number of foreign operations | item	0
Interest Rate Contract [Member] | Cash Flow Hedging [Member]
Significant Accounting Policies [Line Items]
Cash flow hedge gain (loss) to be amortized within 12 months	$ 900
Supplemental Employee Retirement Plan [Member]
Significant Accounting Policies [Line Items]
Number of retirement plans | plan	2
Supplemental Employee Retirement Plan [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, vesting period	5 years
Supplemental Employee Retirement Plan [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, vesting period	10 years
Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, interest credit percentage	4.50%
Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, service credit percentage	3.00%
Supplemental Retirement Plan, Defined Contribution Plan, New Balance Annual Additions [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, service credit percentage	5.00%
Supplemental Retirement Plan, Defined Contribution Plan, Old Balance Annual Additions [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, interest credit percentage	7.50%
Savings and Investment Plan, Defined Contribution Plan [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, minimum annual employee contributions per employee, percent	1.00%
Defined contribution plan, vesting period	5 years
Defined contribution plan, employer matched rate of employee contributions, percentage	50.00%
Defined contribution plan, employer matching contribution, percent	6.00%
Retirement Plan [Member]
Significant Accounting Policies [Line Items]
Defined benefit plan, interest credit rate	4.50%
Defined benefit plan, vesting period (years)	3 years
Retirement Plan [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Defined benefit plan, service credit percentage	3.00%
Retirement Plan [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Defined benefit plan, service credit percentage	5.00%
Share Options [Member]
Significant Accounting Policies [Line Items]
Maximum term of option award (years)	10 years
Share-based Payment Arrangement, Employee [Member]
Significant Accounting Policies [Line Items]
Vesting period (years) for share options and awards	3 years
Share-based Payment Arrangement, Employee [Member] | Service-Based Share Awards [Member]
Significant Accounting Policies [Line Items]
Vesting period (years) for share options and awards	3 years
Share-based Payment Arrangement, Employee [Member] | Market-Based Awards Relative To FTSE NAREIT U.S. Shopping Center Index [Member]
Significant Accounting Policies [Line Items]
Percentage allocation of market based awards	50.00%
Share-based Payment Arrangement, Employee [Member] | Market-Based Awards Relative To Three-Year Absolute Total Shareholder Return [Member]
Significant Accounting Policies [Line Items]
Percentage allocation of market based awards	50.00%
Market based awards, hurdle comparison	6.00%
Share-based Payment Arrangement, Employee [Member] | Market Based Awards [Member]
Significant Accounting Policies [Line Items]
Vesting period (years) for share options and awards	3 years
Building [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Real estate asset, estimated useful life	18 years
Building [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Real estate asset, estimated useful life	40 years
Parking Lot Surfacing And Equipment [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Real estate asset, estimated useful life	10 years
Parking Lot Surfacing And Equipment [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Real estate asset, estimated useful life	20 years
Tenant Base [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Number of customers | customer	2
Concentrations of risk	2.60%
Single Purpose Entities [Member]
Significant Accounting Policies [Line Items]
Single purpose entity, ownership percentage	100.00%
Ninety-Day London Interbank Offered Rate (LIBOR) [Member] | Supplemental Retirement Plan, Defined Contribution Plan, Old Balance Annual Additions [Member]
Significant Accounting Policies [Line Items]
Defined contribution plan, basis spread on variable rate	0.50%
HOUSTON | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Concentrations of risk	20.60%
OTHER PARTS OF TEXAS | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Concentrations of risk	9.80%
FLORIDA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Concentrations of risk	20.40%
CALIFORNIA | Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Significant Accounting Policies [Line Items]
Concentrations of risk	16.40%
COVID-19 [Member]
Significant Accounting Policies [Line Items]
Accrued Rent, Accrued Contract Receivables and Accounts Receivable, net	$ 9,600
Rent forgiveness	3,200
Adjustment to revenue related to potentially uncollectible revenues and disputed amounts	36,100
Straight Line Rent Receivables [Member]
Significant Accounting Policies [Line Items]
Adjustment to revenue related to potentially uncollectible revenues and disputed amounts	$ 15,000