Share Incentive Plans - Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation information
Compensation Expense	$ 27,132	$ 24,997	$ 30,530
Compensation Capitalized	1,218	1,076	2,726
Restricted Units In-Lieu of Bonus	4,418	1,809	4,022
Compensation Equity	32,768	27,882	37,278
Dividends Incurred	1,717	1,502	14,256
Restricted Shares [Member]
Compensation information
Compensation Expense	7,406	9,209	13,539
Compensation Capitalized	852	568	1,477
Restricted Units In-Lieu of Bonus	0	0	0
Compensation Equity	8,258	9,777	15,016
Dividends Incurred	754	761	6,494
Restricted Stock Units (RSUs) [Member]
Compensation information
Compensation Expense	12,310	10,214	13,567
Compensation Capitalized	36	119	591
Restricted Units In-Lieu of Bonus	1,663	190	4,022
Compensation Equity	14,009	10,523	18,180
Dividends Incurred	963	741	7,762
Employee Stock Option [Member]
Compensation information
Compensation Expense	6,683	4,893	2,839
Compensation Capitalized	296	323	593
Restricted Units In-Lieu of Bonus	2,755	1,619	0
Compensation Equity	9,734	6,835	3,432
Dividends Incurred	0	0	0
Employee Share Purchase Plan Discount [Member]
Compensation information
Compensation Expense	733	681	585
Compensation Capitalized	34	66	65
Restricted Units In-Lieu of Bonus	0	0	0
Compensation Equity	767	747	650
Dividends Incurred	$ 0	$ 0	$ 0