Share-Based Compensation (Schedule of Share-Based Compensation Information) (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation [Abstract]
Expense relating to share/unit grants	$ 3,954,000	$ 4,496,000	$ 4,217,000
Amounts capitalized	(231,000)	(379,000)	(454,000)
Total charged to operations	$ 3,723,000	$ 4,117,000	$ 3,763,000
Unvested shares/units, December 31, 2019	645,000
Restricted share grants	63,000
Vested during period	(59,000)
Forfeitures/cancellations	(7,000)
Unvested shares/units, December 31, 2020	642,000	645,000
Unvested shares/unit, December 31, 2019, weighted average grant date fair value	$ 27.92
Restricted share grants, weighted average grant date fair value	17.48
Vested during period, weighted average grant date fair value	37.73
Forfeitures/cancellations, weighted average grant date fair value	40.38
Unvested shares/unit, December 31, 2020, weighted average grant date fair value	$ 25.86	$ 27.92

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost capitalized for award under share-based payment arrangement.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Amount of cost expensed and capitalized for award under share-based payment arrangement.

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