INVESTMENT OPERATIONS - Schedule of Amortized Cost and Fair Value of the Company's Investments Classified as Held-to-Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Fair Value	$ 2,930,737	$ 3,025,790
Fixed maturities
Schedule of Investments [Line Items]
Amortized Cost	2,775,710	2,823,881
Gross Unrecognized Holding Gains	155,027	201,909
Gross Unrecognized Holding Losses	0	0
Fair Value	2,930,737	3,025,790
Fixed maturities \| Red Mountain, LLC
Schedule of Investments [Line Items]
Amortized Cost	804,710	795,881
Gross Unrecognized Holding Gains	54,013	81,022
Gross Unrecognized Holding Losses	0	0
Fair Value	858,723	876,903
Fixed maturities \| Steel City, LLC
Schedule of Investments [Line Items]
Amortized Cost	1,971,000	2,028,000
Gross Unrecognized Holding Gains	101,014	120,887
Gross Unrecognized Holding Losses	0	0
Fair Value	$ 2,072,014	$ 2,148,887

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

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Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563

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