Inventories (Components Of Inventories) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventories [Abstract]
Raw materials			$ 37,660	$ 38,383
Work in process			3,906	3,109
Finished goods and parts			62,337	61,839
Inventories, net			103,903	103,331
Lower of cost or market adjustment	$ 12,900	$ 10,700	$ 12,883	$ 11,053	$ 21,550