Segment Reporting (Schedule Of Underwriting Results For Operating Segments To Income (Loss) Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting [Abstract]
Underwriting gain (loss)	$ 154,828	$ 198,609	$ 574,478	$ 621,569
Net investment income	115,511	142,143	363,140	396,524
Net realized capital gains (losses)	(159,971)	(9,448)	(194,654)	70,694
Net derivative gain (loss)	(11,428)	1,855	(5,225)	3,968
Corporate expenses	(5,924)	(9,958)	(17,312)	(18,802)
Interest, fee and bond issue cost amortization expense	(8,990)	(12,424)	(27,006)	(28,970)
Other income (expense)	17,413	11,332	59,561	(5,835)
INCOME (LOSS) BEFORE TAXES	$ 101,439	$ 322,109	$ 752,982	$ 1,039,148