Fair-Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Interest expense		$ 20,242	$ 18,602	$ 15,541
Interest Rate Swap [Member]
Derivative [Line Items]
Interest expense		500	800	$ 1,900
Interest Rate Swap Buyouts [Member]
Derivative [Line Items]
Interest expense			$ 700
Interest income		$ 600
Interest Rate Swap Buyouts [Member] | Subsequent Event [Member]
Derivative [Line Items]
Interest expense	$ 500