Schedule II - Condensed Financial Information Of The Registrant (Condensed Statements Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income (loss)	$ (80,486)	$ 610,754	$ 806,989
Equity in retained (earnings) deficit of subsidiaries	(56,549)	(71,493)	20,575
Change in other assets and liabilities, net	214,701	(104,276)	(109,004)
Amortization of bond premium (accrual of bond discount)	47,872	46,095	32,172
Realized capital losses (gains)	(6,923)	(101,911)	2,312
Non-cash compensation expense	17,693	14,786	13,347
Net cash provided by (used in) operating activities	659,520	918,475	784,738
Proceeds from fixed maturities matured/called - available for sale, at market value	1,702,973	1,717,659	1,203,548
Proceeds from fixed maturities sold - available for sale, at market value	1,732,246	1,632,719	311,273
Cost of fixed maturities acquired - available for sale, at market value	(3,238,113)	(2,766,212)	(3,051,012)
Net change in short-term investments	100,969	(110,241)	1,228,032
Net cash provided by (used in) investing activities	(208,706)	(270,013)	(372,356)
Common shares issued during the period, net	12,269	3,066	7,284
Purchase of treasury shares	(92,490)	(398,554)	(190,597)
Dividends paid to shareholders	(103,848)	(108,477)	(116,857)
Net cash provided by (used in) financing activities	(234,069)	(653,965)	(383,196)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(26,502)	16,313	12,718
Net increase (decrease) in cash	190,243	10,810	41,904
Cash, beginning of period	258,408	247,598	205,694
Cash, end of period	448,651	258,408	247,598
Registrant [Member]
Net income (loss)	(80,486)	610,754	806,988
Equity in retained (earnings) deficit of subsidiaries	71,233	(618,906)	(829,335)
Dividends received from subsidiaries	190,000	215,000	350,000
Change in other assets and liabilities, net	(718)	2,849	(1,619)
Increase (decrease) in due to/from affiliates	224	(291)	750
Amortization of bond premium (accrual of bond discount)	875	733	80
Realized capital losses (gains)		(7)	15,142
Non-cash compensation expense	936	813	641
Net cash provided by (used in) operating activities	182,064	210,945	342,647
Additional investment in subsidiaries	(91,548)	(28,619)	(287,114)
Proceeds from fixed maturities matured/called - available for sale, at market value	9,219	4,211	3,672
Proceeds from fixed maturities sold - available for sale, at market value		7	227,298
Cost of fixed maturities acquired - available for sale, at market value		(81,113)	(20,577)
Net change in short-term investments	30,180	4,774	(4,621)
Net cash provided by (used in) investing activities	(52,149)	(100,740)	(81,342)
Common shares issued during the period, net	29,025	17,038	19,990
Purchase of treasury shares	(54,879)	(18,963)	(164,757)
Dividends paid to shareholders	(103,848)	(108,477)	(116,856)
Net cash provided by (used in) financing activities	(129,702)	(110,402)	(261,623)
Net increase (decrease) in cash	213	(197)	(318)
Cash, beginning of period	49	246	564
Cash, end of period	262	49	246
Purchase of treasury shares by subsidiary	$ 37,611	$ 379,591	$ 25,840