Stock-Based Compensation - Narrative (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) installment shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	3,400,000
Number of full value shares counted against overall limits of the stock incentive plan (in shares)	2
Number of shares counted against overall limits of the stock incentive plan, vesting in over five years (in shares)	1
Awards granted to key employees (in shares)	898,000	800,000	704,000
Stock-based compensation expense \| $	$ 22,299	$ 18,478	$ 17,448
Capitalized stock-based compensation \| $	5,006	$ 2,537	$ 1,503
Unrecognized compensation cost related to nonvested options and LTIP unit awards \| $	$ 19,400
Unrecognized compensation cost related to nonvested options and LTIP unit awards, recognition period	2 years
Non-employee director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-employee director awards granted in lieu of cash compensation (in shares)	37,000	28,000	35,000
LTIP Units \| Various employees \| Vesting tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of annual vesting installments \| installment	3
LTIP Units \| Various employees \| Vesting tranche two \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
LTIP Units \| Various employees \| Vesting tranche two \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years

Awards granted to key employees.

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Non-employee director awards granted in lieu of cash compensation.

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- Definition

Number Of Shares Counted Against Stock Incentive Plan Limits For Each Full Value Award

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Number Of Shares Counted Against Stock Incentive Plan Limits For Stock Appreciation Rights and Options With Terms of More Than Five Years

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Share-based Compensation Arrangement by Share-based Payment Award, Number Of Annual Installments

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- Definition

Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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