INVESTMENTS (Equity Securities) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Cost	$ 356,176	$ 398,956
Gross unrealized gains	64,595	81,521
Gross unrealized losses	(2,885)	(6,270)
Fair value	$ 417,886	474,207
Limited partnership
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment composition	62.00%
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Cost	$ 10,679	504
Gross unrealized gains	35	77
Gross unrealized losses	(1,419)	(388)
Fair value	9,295	193
Preferred shares
Debt and Equity Securities, FV-NI [Line Items]
Cost	6,249	0
Gross unrealized gains	1,505	0
Gross unrealized losses	0	0
Fair value	7,754	0
Exchange-traded funds
Debt and Equity Securities, FV-NI [Line Items]
Cost	141,748	215,986
Gross unrealized gains	51,920	81,444
Gross unrealized losses	(1,466)	(105)
Fair value	192,202	297,325
Bond mutual funds
Debt and Equity Securities, FV-NI [Line Items]
Cost	197,500	182,466
Gross unrealized gains	11,135	0
Gross unrealized losses	0	(5,777)
Fair value	$ 208,635	$ 176,689

Percentage Of Investment Composition

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- Definition

Amount of 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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

+ References

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Amount of unrealized gain 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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714

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Amount of unrealized 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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