Segment Reporting (Schedule Of Underwriting Results For Operating Segments To Income (Loss) Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net investment income	$ 102,524	$ 122,566
Net realized capital gains (losses)	(74,259)	(10,505)
Net derivative gain (loss)	(3,020)	(242)
Corporate expenses	(7,886)	(5,463)
Interest, fee and bond issue cost amortization expense	(9,228)	(8,990)
Other income (expense)	2,066	(51,281)
INCOME (LOSS) BEFORE TAXES	177,067	364,145
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Underwriting gain (loss)	171,002	215,498
Net investment income	102,524	122,566
Net realized capital gains (losses)	(74,259)	(10,505)
Net derivative gain (loss)	(3,020)	(242)
Corporate expenses	(7,886)	(5,463)
Interest, fee and bond issue cost amortization expense	(9,228)	(8,990)
Other income (expense)	(2,066)	51,281
INCOME (LOSS) BEFORE TAXES	$ 177,067	$ 364,145