Investments - Net Investment Gains (Losses) By Transaction Type (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Credit impairment write-downs	$ 0	$ 0	$ 0	$ 0
Change in intent write-downs	(1,057)	(5)	(5,272)	(276)
Net other-than-temporary impairment losses on securities recognized in net income	(1,057)	(5)	(5,272)	(276)
Sales and other, net	3,736	608	8,645	147,513
Change in fair value - equity securities	2,242	1,081	(5,644)	8,029
Change in fair value and gains (losses) realized on settlements - derivatives	(2,452)	(3,840)	(10,562)	(3,672)
Net investment gains (losses)	$ 2,469	$ (2,156)	$ (12,833)	$ 151,594

Other than Temporary Impairment Losses, Investments, Portion Recognized In Earnings, Change In Intent

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Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

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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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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.

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Amount of other-than-temporary impairment (OTTI) on investment in debt security, recognized in earnings.

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Amount of realized gain (loss) on investment.

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