Income Taxes (Reconciliation Of The Difference Between The Provision For Income Taxes And The Expected Tax Provision At The Weighted Average Tax Rate) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Underwriting gain (loss)									$ 738,608	$ 259,003	$ (757,781)
Net investment income	126,127	127,872	148,729	145,781	146,411	152,024	149,329	152,438	548,509	600,202	620,041
Net realized capital gains (losses)	94,629	44,958	33,905	126,735	19,518	62,743	(16,580)	98,719	300,227	164,400	6,923
Net derivative gain (loss)									44,044	(9,738)	(11,261)
Corporate expenses									(24,817)	(23,976)	(16,461)
Interest, fee and bond issue cost amortization expense									(46,118)	(53,683)	(52,319)
Other income (expense)									(5,487)	3,318	(23,089)
INCOME (LOSS) BEFORE TAXES									1,554,966	939,526	(233,947)
Increase (decrease) in taxes resulting from: Other										(17,520)
Total income tax expense (benefit)									289,706	110,572	(153,461)
U.S. [Member]
Income Taxes [Line Items]
Underwriting gain (loss)									246,699	42,775	(574,142)
Net investment income									274,920	287,382	292,980
Net realized capital gains (losses)									295,814	143,326	(28,565)
Corporate expenses									(8,262)	(8,764)	(6,073)
Interest, fee and bond issue cost amortization expense									(45,452)	(50,746)	(50,763)
Other income (expense)									(7,086)	18,360	(28,644)
INCOME (LOSS) BEFORE TAXES									756,633	432,332	(395,206)
Expected tax provision at the applicable statutory rate(s)									264,822	151,316	(138,322)
Increase (decrease) in tax resulting from: Tax exempt income									(15,038)	(20,623)	(33,672)
Increase (decrease) in tax resulting from: Dividend received deduction									(7,809)	(8,351)	(6,893)
Increase (decrease) in tax resulting from: Proration									2,274	3,138	5,080
Increase (decrease) in tax resulting from: Tax audit settlement										(2,508)	(710)
Increase (decrease) in tax resulting from: Uncertain tax position release										(31,912)	8,139
Increase (decrease) in taxes resulting from: Other									27,238	5,381	(1,471)
Total income tax expense (benefit)									271,487	96,441	(167,849)
Non-U.S. [Member]
Income Taxes [Line Items]
Underwriting gain (loss)									491,909	216,228	(183,641)
Net investment income									273,589	312,820	327,062
Net realized capital gains (losses)									4,413	21,073	35,488
Net derivative gain (loss)									44,044	(9,738)	(11,261)
Corporate expenses									(16,555)	(15,211)	(10,388)
Interest, fee and bond issue cost amortization expense									(665)	(2,936)	(1,556)
Other income (expense)									1,598	(15,042)	5,556
INCOME (LOSS) BEFORE TAXES									798,333	507,194	161,260
Expected tax provision at the applicable statutory rate(s)									16,279	11,012	12,216
Increase (decrease) in taxes resulting from: Other									1,940	3,119	2,172
Total income tax expense (benefit)									$ 18,219	$ 14,131	$ 14,388