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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(b))
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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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Aggregate carrying value of owned private equity or other securities for which a quoted market price is not readily determinable, the value of which has been determined by management based upon fair value methods, including pricing of similar securities and valuation techniques and is included in the schedule of financial condition or the balance sheet.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Investments and Fair Value Measurements Investments in Privately Held Companies (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Apr. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Equity securities under the equity method investment	$ 47,996		$ 54,606
Equity securities without readily determinable fair values	$ 9,862		0
Fair Value, Measurements, Recurring \| Short-term notes receivable
Schedule of Available-for-sale Securities [Line Items]
Short-term notes receivable			4,476
Level 3 \| Fair Value, Measurements, Recurring \| Short-term notes receivable
Schedule of Available-for-sale Securities [Line Items]
Short-term notes receivable		$ 4,900	$ 4,476