Property and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation	$ 50,389	$ 55,962	$ 54,826
Operating Equipment [Member]
Property, Plant and Equipment [Line Items]
Operating equipment excluded from property and equipment held for sale		$ 3,537	$ 8,460