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Investments (Realized and Unrealized Gains (Losses) on Equity Securities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Gain (Loss) on Securities [Line Items]
Unrealized (losses) gains recognized in income on equity securities on securities remaining in our portfolio at March 31, 2020	$ (17,140)	$ 12,055
Unrealized (losses) gains recognized in income on equity securities on securities sold in each respective period	3	(1,944)
Total unrealized (losses) gains recognized in income on equity securities	$ (17,137)	$ 10,111

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- Definition

The unrealized gains (losses) on equity securities sold during the period.

+ References

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- Definition

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).

+ References

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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- Definition

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.

+ References

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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