Equity Method Investment (Details) - eREX Spark ¥ in Millions, $ in Millions	1 Months Ended	12 Months Ended
Sep. 30, 2015 USD ($)	Sep. 30, 2015 JPY (¥)	Dec. 31, 2017 USD ($) director
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investment	$ 1.4	¥ 156.4
Ownership percentage			20.00%
Dividends distributed percentage			30.00%
Number of years dividend is paid thereafter			4 years
Number of Board of Directors \| director			4
Number of Board of Directors appointed by the company \| director			1
Board of Director members' percentage			25.00%
Equity method investment \| $			$ 2.5
Share in equity method investment earnings \| $			$ 0.2

Equity Method Investment, Board of Director Members, Percentage

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Equity Method Investment, Dividends or Distributions, Entitled Period

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Number of Board of Directors

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Number of Board of Directors Appointed by the Company

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Proceeds from Equity Method Investment, Dividends or Distributions, Percentage

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

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-Section S99
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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

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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.

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