Debt (Schedule of Interest Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Interest Expense [Abstract]
Interest expense	$ 11,414	$ 10,312	$ 21,941	$ 20,345
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	76	645	352	1,434
Interest Costs Capitalized Adjustment	(47)	(93)	(71)	(160)
Amortization of debt issuance costs, debt discount and premium	777	868	1,612	1,774
Total interest expense	$ 12,220	$ 11,732	$ 23,834	$ 23,393