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	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Net investment income	$ 110,685	$ 115,511	$ 125,046	$ 122,583	$ 134,046	$ 142,143	$ 131,224	$ 123,157	$ 473,825	$ 530,570	$ 548,509
Net realized capital gains (losses)	$ 10,507	$ (159,971)	$ (24,178)	$ (10,505)	$ 13,352	$ (9,448)	$ 59,016	$ 21,126	(184,147)	84,046	300,227
Net derivative gain (loss)									6,317	(11,599)	44,044
Corporate expenses									(23,254)	(23,421)	(24,817)
Interest, fee and bond issue cost amortization expense									(36,191)	(38,533)	(46,118)
Other income (expense)									60,435	18,437	(5,487)
INCOME (LOSS) BEFORE TAXES									1,208,509	1,446,115	1,554,966
Total income tax expense (benefit)									134,021	187,652	289,706
U.S. [Member]
Income Taxes [Line Items]
Underwriting gain (loss)									294,386	228,194	246,699
Net investment income									234,709	260,501	274,920
Net realized capital gains (losses)									(159,268)	78,006	295,814
Corporate expenses									(7,179)	(7,252)	(8,262)
Interest, fee and bond issue cost amortization expense									(35,434)	(37,970)	(45,452)
Other income (expense)									27,706	(1,561)	(7,086)
INCOME (LOSS) BEFORE TAXES									354,920	519,918	756,633
Expected tax provision at the applicable statutory rate(s)									124,221	181,972	264,822
Increase (decrease) in tax resulting from: Tax exempt income									(10,004)	(12,231)	(15,038)
Increase (decrease) in tax resulting from: Dividend received deduction									(5,364)	(5,910)	(7,809)
Increase (decrease) in tax resulting from: Proration									2,160	1,835	2,274
Increase (decrease) in taxes resulting from: Other									8,197	(588)	27,238
Total income tax expense (benefit)									119,210	165,077	271,487
Non-U.S. [Member]
Income Taxes [Line Items]
Underwriting gain (loss)									617,137	658,421	491,909
Net investment income									239,115	270,069	273,589
Net realized capital gains (losses)									(24,879)	6,040	4,413
Net derivative gain (loss)									6,317	(11,599)	44,044
Corporate expenses									(16,075)	(16,169)	(16,555)
Interest, fee and bond issue cost amortization expense									(756)	(563)	(665)
Other income (expense)									32,730	19,998	1,598
INCOME (LOSS) BEFORE TAXES									853,589	926,197	798,333
Expected tax provision at the applicable statutory rate(s)									14,848	21,279	16,279
Increase (decrease) in taxes resulting from: Other									(37)	1,296	1,940
Total income tax expense (benefit)									14,811	22,575	18,219
Parent Company [Member]
Income Taxes [Line Items]
Net investment income									3,895	824	982
Net realized capital gains (losses)									(3,057)	15
Interest, fee and bond issue cost amortization expense									(4,300)
Other income (expense)									(459)	(574)	(902)
INCOME (LOSS) BEFORE TAXES									$ 977,869	$ 1,199,156	$ 1,259,382
Total income tax expense (benefit)