Share and Unit-Based Plans - Compensation cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 3,315	$ 4,616	$ 13,353	$ 28,219
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	2,498	3,440	8,859	21,823
Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	632	972	3,836	5,717
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	0	32	51	94
Phantom Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost under share and unit-based plans	$ 185	$ 172	$ 607	$ 585