INVESTMENT OPERATIONS - Summary of Net Realized Investment Gains (Losses) for All Other Investments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Fixed maturities	$ 5,137	$ 2,783
Equity gains and losses	30,635	(8,738)
Modco trading portfolio	94,902	(84,709)
Other investments	(1,146)	3,113
Realized gains (losses) - all other investments	129,528	(87,551)
Realized gains (losses) - derivatives	(73,308)	46,826
Realized investment gains (losses)	56,220	(40,725)
Net impairments losses recognized in earnings	$ (3,142)	$ (3,645)

Realized Investment Gains (Losses), All Investments

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Represents the total realized gain (loss) included in earnings during the period as a result of investments other than derivative financial instruments, net of the amount recognized in earnings for other than temporary impairments (OTTI) of investments in debt and equity securities.

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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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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).

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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Amount of gain (loss) included in earnings for investments classified as other.

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Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings and other comprehensive loss (OCI).

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