Investments (Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Municipal bonds (tax-exempt)	$ 16,601	$ 18,826
Short-term investments, including overnight deposits	10,243	10,212
Dividends on equity securities	28,614	25,786
Income (loss) from equity method investments	(19,979)	1,896
Other	757	2,301
Total investment income	93,103	118,381
Investment expenses	(4,860)	(4,199)
Net investment income	88,243	114,182
Municipal Bonds (taxable) [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	16,895	18,579
Other taxable bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	$ 39,972	$ 40,781