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Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions | 3 Months Ended
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Mar. 31, 2018 USD ($) Segment
Accounting Policies [Abstract] |
Unrealized gains related to Marketable securities and Investments carried under measurement alternative | $ | $ 2.6
Number of operating segment | Segment | 1

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- References No definition available. + Details
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- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References No definition available. + Details
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- Definition The aggregate net change in the difference between the fair value and the carrying value, or in the comparative fair values, of marketable securities categorized as trading held at each balance sheet date, that was included in earnings for the period, which may have arisen from (a) securities classified as trading, (b) the unrealized holding gain (loss) on held-to-maturity securities transferred to the trading security category, and (c) the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) on available-for-sale securities transferred to trading securities during the period and/or any unrealized gains or losses on investments that are separately or otherwise not categorized as trading or available-for-sale. + References No definition available. + Details
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