Investments (Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Dividends on equity securities	$ 31,134	$ 25,962	$ 84,968	$ 74,289
Total investment income	196,266	116,549	534,070	314,093
Investment expenses	(4,059)	(3,935)	(12,835)	(12,380)
Net investment income	192,207	112,614	521,235	301,713
Fixed Maturities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	98,891	72,477	269,438	215,541
Short-term investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	26,768	10,316	77,099	14,644
Cash and Cash Equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Interest income	$ 39,473	$ 7,794	$ 102,565	$ 9,619

Amount of dividend income on nonoperating securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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