Investments - Portion of Net Unrealized Gains and Losses Recognized During the Reporting Period Related To Equity Securities (Details) - Equity securities - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Equity securities:
Net (losses) gains recognized during the period	$ (11,422)	$ 585
Less: net losses recognized on securities sold	(37)	0
Net unrealized (losses) gains recognized on securities held at reporting date	$ (11,385)	$ 585

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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