Financial Instruments (Details Textual 2) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Strategic Investments
Business Acquisition [Line Items]
Strategic investment portfolio	$ 85.8	$ 99.9

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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