Investments (Summary Of Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 62,904	$ 59,110
Funds held interest income (expense)	1,939	2,654
Interest income from Parent	1,075	1,075
Gross investment income	65,918	62,839
Investment expenses	(5,069)	(4,394)
Net investment income	60,849	58,445
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	46,980	45,326
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	6,748	9,148
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	390	304
Limited Partnerships [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	(224)	(2,514)
Dividends From Preferred Shares Of Affiliate [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	7,758	7,758
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 1,252	$ (912)