INVESTMENTS - Equity securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost	$ 528,864	$ 421,744
Gross unrealized gains	135,230	97,648
Gross unrealized losses	(8,419)	(947)
Fair value	$ 655,675	518,445
Limited Partner
Debt and Equity Securities, FV-NI [Line Items]
Percentage of investment composition (as a percent)	71.00%
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost	$ 1,264	10,810
Gross unrealized gains	585	689
Gross unrealized losses	(485)	(557)
Fair value	1,364	10,942
Preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost	115	6,301
Gross unrealized gains	64	1,767
Gross unrealized losses	0	0
Fair value	179	8,068
Exchange-traded funds
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost	203,455	147,794
Gross unrealized gains	134,037	74,314
Gross unrealized losses	(677)	(390)
Fair value	336,815	221,718
Bond mutual funds
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost	324,030	256,839
Gross unrealized gains	544	20,878
Gross unrealized losses	(7,257)	0
Fair value	$ 317,317	$ 277,717

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), classified as current.

+ 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=123594786&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=123583765&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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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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