Fair Value of Derivative and Other Financial Instruments - Investments in NDT and Gross Realized Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Equity securities:
Net gains (losses) from equity securities sold	$ 2,792	$ (1,061)	$ 1,947	$ 3,945
Net gains (losses) from equity securities still held	1,142	(26,224)	8,619	(48,259)
Total net gains (losses) on equity securities	3,934	(27,285)	10,566	(44,314)
Available-for-sale debt securities:
Net (losses) on debt securities	(157)	(14,510)	(347)	(24,054)
Net gains (losses) on investment securities	$ 3,777	$ (41,795)	$ 10,219	$ (68,368)

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Amount of unrealized and realized gain (loss) on investment 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 other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

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