Investments (Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	$ 13,891	$ (36,093)	$ (4,604)	$ (38,159)
Change in fair value of securities sold during the period	(6,652)	2,683	(11,263)	16,706
Change in fair value of securities held at the end of the period	910,291	(232,507)	1,705,661	612,626
Total change in fair value of equity securities	903,639	(229,824)	1,694,398	629,332
Net investment gains (losses)	917,530	(265,917)	1,689,794	591,173
Change in net unrealized losses on available-for-sale investments included in other comprehensive income (loss):	551,244	(208,405)	358,877	(170,606)
Fixed Maturity Securities [Member]
Gain (Loss) on Securities [Line Items]
Change in net unrealized losses on available-for-sale investments included in other comprehensive income (loss):	546,386	(208,598)	361,659	(167,411)
Short-term investments [Member]
Gain (Loss) on Securities [Line Items]
Change in net unrealized losses on available-for-sale investments included in other comprehensive income (loss):	$ 4,858	$ 193	$ (2,782)	$ (3,195)