Segment Reporting (Schedule Of Underwriting Results For Operating Segments To Income (Loss) Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting [Abstract]
Underwriting gain (loss)	$ 182,869	$ 194,519	$ 419,650	$ 422,960
Net investment income	125,046	131,224	247,629	254,381
Net realized capital gains (losses)	(24,178)	59,016	(34,683)	80,142
Net derivative gain (loss)	6,445	3,774	6,203	2,113
Corporate expenses	(5,925)	(3,899)	(11,388)	(8,844)
Interest, fee and bond issue cost amortization expense	(9,026)	(8,978)	(18,016)	(16,546)
Other income (expense)	(3,925)	(13,871)	42,148	(17,167)
INCOME (LOSS) BEFORE TAXES	$ 271,306	$ 361,785	$ 651,543	$ 717,039