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.

+ Details

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- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=109979856&loc=SL6284422-111562

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities owned not readily marketable	$ 45,500		$ 45,500		$ 37,500
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other than temporary impairment losses, investments	$ 0	$ 0	$ 0	$ 0