Share and Unit-Based Plans - Compensation cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 4,210	$ 3,373	$ 9,813	$ 10,038
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	3,350	2,647	6,564	6,361
Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	694	544	2,896	3,204
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	0	0	0	51
Phantom Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 166	$ 182	$ 353	$ 422