Derivative Instruments (Schedule of Derivative Instruments, Effect on other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Amount of gain/(loss) recognized in OCI	$ 692	$ 2,479	$ (4,126)
Total amount of Interest Expense presented in the consolidated statements of income	(61,023)	(68,124)	(64,860)
Total amount of Loss on Extinguishment of Debt presented in the consolidated statements of income (1)	(1,680)	0	0
Write off of deferred debt issuance cost	400
Interest rate swaps
Derivative [Line Items]
Total amount of Interest Expense presented in the consolidated statements of income	(61,023)	(68,124)	(64,860)
Interest Expense | Interest rate swaps
Derivative [Line Items]
Amount of gain/(loss) recognized in OCI	692	2,479	(4,126)
Amount of gain/(loss) reclassified from OCI	1,558	(3,502)	(4,548)
Gain (Loss) On Extinguishment Of Debt | Interest rate swaps
Derivative [Line Items]
Amount of gain/(loss) reclassified from OCI	$ (1,258)	$ 0	$ 0