Business and Basis of Presentation (Revenue Recognition) (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cost of sales \| $	$ 102,780	$ 102,179	$ 101,885	$ 113,357	$ 114,708	$ 122,941	$ 113,928	$ 113,097	$ 420,201	$ 464,674	$ 381,774
Number of operating segments \| segment									2

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration