Investments (Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Municipal bonds (tax-exempt)	$ 18,826	$ 20,935
Short-term investments, including overnight deposits	10,212	10,590
Dividends on equity securities	25,786	24,007
Income from equity method investments	1,896	1,778
Other	2,301	(110)
Total investment income	118,381	112,302
Investment expenses	(4,199)	(4,286)
Net investment income	114,182	108,016
Taxable Municipal Bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	18,579	17,633
Other Taxable Bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	$ 40,781	$ 37,469