Segment Reporting (Schedule Of Underwriting Results For The Operating Segments To Income Before Taxes) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting [Abstract]
Underwriting gain (loss)									$ (757,781)	$ (109,200)	$ 424,529
Net investment income	126,253	156,465	158,618	178,705	184,865	141,368	165,731	161,499	620,041	653,463	547,793
Net realized capital gains (losses)	137,283	(137,671)	(4,845)	12,156	32,591	38,295	(41,693)	72,718	6,923	101,911	(2,312)
Realized gain on debt repurchase											78,271
Net derivative gain (loss)									(11,261)	(1,119)	3,204
Corporate expenses									(16,461)	(14,914)	(17,607)
Interest, fee and bond issue cost amortization expense									(52,319)	(55,830)	(72,081)
Other income (expense)									(23,089)	16,927	(22,476)
INCOME (LOSS) BEFORE TAXES									$ (233,947)	$ 591,238	$ 939,321