Fair-Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Interest expense (income)	$ 4,288	$ 4,328
Interest Rate Current Swap [Member]
Derivative [Line Items]
Interest expense (income)	500	400
Interest Rate Swap Buyouts [Member]
Derivative [Line Items]
Interest expense (income)	$ (200)	$ 200