Investments (Summary Of Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 67,276	$ 66,651	$ 202,845	$ 214,916
Funds held interest income (expense)	1,090	940	4,718	4,326
Interest income from Parent	1,075	1,075	3,225	3,225
Gross investment income	69,441	68,666	210,788	222,467
Investment expenses	(4,871)	(5,303)	(13,901)	(15,598)
Net investment income	64,570	63,363	196,887	206,869
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	44,810	46,414	134,931	140,829
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	7,870	8,004	25,752	26,638
Short-Term Investments And Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	296	220	851	705
Limited Partnerships [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	6,020	3,021	17,698	17,676
Dividends From Parent's Shares [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment		9,234		27,702
Dividends From Preferred Shares Of Affiliate [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	7,758		23,274
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross investment income before adjustment	$ 522	$ (242)	$ 339	$ 1,366