Related Parties (Narrative) (Details) - WAVE [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Percentage of ownership in joint venture	50.00%
Purchases from joint venture	$ 22.5	$ 18.2	$ 18.0
Reimbursement from joint venture	15.8	14.9	$ 9.1
Due from related parties	$ 3.0	$ 2.6

For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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