Long-Term Incentive Plan (Equity-Based Incentive Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Allocation of LTIP expense on consolidated statements of income	$ 4,914	$ 6,632
G&A Expense [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Allocation of LTIP expense on consolidated statements of income	4,871	6,577
Operating Expenses [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Allocation of LTIP expense on consolidated statements of income	43	55
Performance Based Awards [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Allocation of LTIP expense on consolidated statements of income	3,644	5,924
Time-Based Awards [Member]
Share-based Compensation Arrangements by Share-based Payment Award [Line Items]
Allocation of LTIP expense on consolidated statements of income	$ 1,270	$ 708