Investments (Details) - Certificates of deposit	6 Months Ended
Jun. 30, 2017
Minimum
Schedule of Held-to-maturity Securities
Investment Term	3 months
Maximum
Schedule of Held-to-maturity Securities
Investment Term	18 months

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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