Share and Unit-Based Plans - Compensation cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 5,603	$ 6,665
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	3,214	3,714
Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	2,202	2,660
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	0	51
Phantom Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 187	$ 240