Schedule II - Condensed Financial Information Of The Registrant (Condensed Statements Of Cash Flows) (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
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 392,374	$ 107,572	$ 235,472	$ 339,070	$ 357,263	$ 301,253	$ 297,925	$ 302,022	$ 1,074,488	$ 1,258,463	$ 1,265,260
Change in other assets and liabilities, net									264	35,419	(57,212)
Amortization of bond premium (accrual of bond discount)									50,901	49,214	66,461
Realized capital losses (gains)	(10,507)	$ 159,971	$ 24,178	10,505	(13,352)	$ 9,448	$ (59,016)	(21,126)	184,147	(84,046)	(300,227)
Non-cash compensation expense									21,237	21,197	31,844
Net cash provided by (used in) operating activities									1,308,382	1,313,821	1,098,261
Proceeds from fixed maturities sold - available for sale, at market value									1,724,093	1,811,801	1,092,387
Cost of fixed maturities acquired - available for sale, at market value									(4,718,303)	(4,672,633)	(3,543,776)
Net change in short-term investments									(98,903)	(497,983)	(357,451)
Net cash provided by (used in) investing activities									(1,121,737)	(1,180,072)	(224,003)
Common shares issued during the period, net									13,597	17,839	51,500
Purchase of treasury shares									(400,059)	(500,024)	(621,915)
Dividends paid to shareholders									(175,107)	(145,913)	(106,681)
Net cash provided by (used in) financing activities									(332,879)	(312,232)	(776,493)
EFFECT OF EXCHANGE RATE CHANGES ON CASH									(7,582)	4,575	(23,433)
Net increase (decrease) in cash									(153,816)	(173,908)	74,332
Cash, beginning of period				437,474				611,382	437,474	611,382	537,050
Cash, end of period	283,658				437,474				283,658	437,474	611,382
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									977,869	1,199,156	1,259,382
Equity in retained (earnings) deficit of subsidiaries									(997,730)	(1,214,334)	(1,275,955)
Dividends received from subsidiaries									590,000	690,000	665,000
Change in other assets and liabilities, net									642	20,612	1,334
Increase (decrease) in due to/from affiliates									839	(2,520)	1,378
Amortization of bond premium (accrual of bond discount)									525	156	241
Realized capital losses (gains)									3,057	(15)
Non-cash compensation expense									1,841	1,828	1,087
Net cash provided by (used in) operating activities									577,043	694,883	652,467
Additional investment in subsidiaries									(60,600)	(73,873)	(93,967)
Subscription advances to Mt. Logan Re											(20,000)
Proceeds from fixed maturities matured/called - available for sale, at market value									26,074	4,765	7,856
Proceeds from fixed maturities sold - available for sale, at market value									252,047	50,010
Cost of fixed maturities acquired - available for sale, at market value									(532,480)	(49,994)	(413)
Net change in short-term investments									279,462	(269,307)	103,174
Net cash provided by (used in) investing activities									(35,497)	(338,399)	(3,350)
Common shares issued during the period, net									32,962	37,208	82,258
Purchase of treasury shares									(400,059)	(500,024)	(621,915)
Proceeds from issuance of long term notes- affiliated										250,000
Dividends paid to shareholders									(175,107)	(145,913)	(106,681)
Net cash provided by (used in) financing activities									$ (542,204)	$ (358,729)	$ (646,338)
EFFECT OF EXCHANGE RATE CHANGES ON CASH
Net increase (decrease) in cash									$ (658)	$ (2,245)	$ 2,779
Cash, beginning of period				$ 1,398				$ 3,643	1,398	3,643	864
Cash, end of period	$ 740				$ 1,398				$ 740	$ 1,398	$ 3,643