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Summary of Accounting policies - Additional Information (Details) | 3 Months Ended
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Mar. 31, 2018 USD ($)
Summary of Accounting Policies [Abstract] |
Cumulative Effect of New Accounting Principle in Period of Adoption | $ 1,498,000
Delay of Revenue Recognition Due To Implementation of New Standard | $ 407,000

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- Definition Delay of Revenue Recognition Due To Implementation of New Standard + References No definition available. + Details
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- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
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