Commitments and Contingencies - Employee Contracts and Severance Costs (Details)	6 Months Ended
Jun. 30, 2018
Employment contracts
Restructuring Cost and Reserve [Line Items]
Maximum term of executive's annual base salary to determine severance obligations	12 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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