Share and Unit-based Plans - Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share and unit-based plans
Compensation cost under share and unit-based plans	$ 33,551	$ 37,005	$ 40,529
Capitalized share and unit-based compensation costs	6,184	6,206	7,241
Stock awards
Share and unit-based plans
Compensation cost under share and unit-based plans	0	0	20
Stock units
Share and unit-based plans
Compensation cost under share and unit-based plans	6,355	6,045	6,305
Unrecognized compensation cost of share and unit-based plans	1,833
LTIP units
Share and unit-based plans
Compensation cost under share and unit-based plans	26,311	30,161	32,957
Unrecognized compensation cost of share and unit-based plans	2,395
Stock options
Share and unit-based plans
Compensation cost under share and unit-based plans	125	85	16
Unrecognized compensation cost of share and unit-based plans	51
Phantom stock units
Share and unit-based plans
Compensation cost under share and unit-based plans	760	714	1,231
Stock awards and units
Share and unit-based plans
Fair value of equity-based awards vested during period	$ 6,479	$ 5,257	$ 5,644

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, 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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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