Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Intangible Assets Goodwill Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Apr. 24, 2017	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 359,688	$ 345,269	$ 8,007	$ 342,111
Addition due to acquisition	8,007
Addition due to purchase accounting adjustments		4,434
Other, including foreign currency translation	6,412	(1,276)
SCEM
Goodwill [Line Items]
Goodwill	304,270	297,858		294,700
Addition due to acquisition	0
Addition due to purchase accounting adjustments		4,434
Other, including foreign currency translation	6,412	(1,276)
MC
Goodwill [Line Items]
Goodwill	8,007	0		0
Addition due to acquisition	8,007
Addition due to purchase accounting adjustments		0
Other, including foreign currency translation	0	0
AMH
Goodwill [Line Items]
Goodwill	47,411	47,411		$ 47,411
Addition due to acquisition	0
Addition due to purchase accounting adjustments		0
Other, including foreign currency translation	$ 0	$ 0