Intangible Assets and Goodwill (Goodwill Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, Foreign Currency Translation Gain (Loss)	$ 4,064	$ (5,746)
Gross Carrying Amount	231,431	226,564
Goodwill, Impaired, Accumulated Impairment Loss	(21,770)	(21,770)
Net Carrying Amount	209,661	204,794	$ 116,899
MID
Goodwill [Line Items]
Goodwill, Foreign Currency Translation Gain (Loss)	0
Gross Carrying Amount	66,643	66,643
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Net Carrying Amount	66,643	66,643	19,905
RSD
Goodwill [Line Items]
Goodwill, Foreign Currency Translation Gain (Loss)	4,064	(5,746)
Gross Carrying Amount	143,018	138,151
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Net Carrying Amount	143,018	138,151	$ 96,994
Other
Goodwill [Line Items]
Gross Carrying Amount	21,770	21,770
Goodwill, Impaired, Accumulated Impairment Loss	(21,770)	(21,770)
Net Carrying Amount	$ 0	$ 0