Schedule II - Condensed Financial Information Of The Registrant (Condensed Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net Investment Income	$ 146,077	$ 181,058	$ 179,028	$ 140,976	$ 140,204	$ 161,363	$ 141,322	$ 138,294				$ 647,139	$ 581,183	$ 542,898
Net realized capital gains (losses)	75,443	(12,943)	30,272	92,232	(172,815)	54,804	15,776	(24,901)				185,004	(127,136)	153,194
Other income (expense)			(18,225)	(3,300)		(13,408)	(6,573)	17,033	$ (21,525)	$ 10,460	$ (2,948)	(11,034)	(24,771)	(21,215)
Total revenues			2,008,727	1,965,836		1,936,463	1,883,330	1,750,126	3,974,563	3,633,456	5,569,919	8,231,169	7,361,495	6,622,298
Interest expense - affiliated												31,693	31,031	31,603
Total claims and expenses	1,976,943	1,933,158	1,620,413	1,537,009	2,481,858	1,731,201	1,817,815	1,511,100				7,132,182	7,603,677	6,202,887
INCOME (LOSS) BEFORE TAXES			372,345	414,544		189,471	51,154	222,612	786,889	273,766	463,237	1,098,987	(242,182)	419,411
Income tax expense (benefit)			(39,477)	(59,993)		8,910	9,633	(7,426)	(99,470)	2,207	11,117	(89,526)	331,223	63,340
NET INCOME (LOSS)	$ 217,644	$ 104,398	332,868	354,551	$ (385,313)	198,381	60,787	215,186	687,419	275,973	474,354	1,009,461	89,041	482,751
Unrealized appreciation (depreciation) ("URA(D)") on securities arising during the period												496,430	(255,656)	(64,348)
Reclassification adjustment for realized losses (gains) included in net income (loss)												(12,613)	27,496	(6,950)
Total URA(D) on securities arising during the period												483,817	(228,160)	(71,298)
Foreign currency translation adjustments												14,030	(76,816)	121,917
Benefit plan actuarial net gain (loss) for the period												(12,591)	(510)	1,027
Reclassification adjustment for amortization of net (gain) loss included in net income (loss)												5,453	5,021	5,477
Total benefit plan net gain (loss) for the period												(7,138)	4,511	6,504
Total other comprehensive income (loss), net of tax												490,709	(300,465)	57,123
COMPREHENSIVE INCOME (LOSS)			$ 504,077	$ 600,997		$ 173,402	$ (42,577)	$ 35,304	$ 1,105,074	$ (7,273)	$ 166,129	1,500,170	(211,424)	539,874
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net Investment Income												3,484	3,790	1,344
Net realized capital gains (losses)												(66)	(57)	80
Other income (expense)												458	(5,299)	(6,872)
Net income (loss) of subsidiaries												1,026,233	112,859	509,279
Total revenues												1,030,109	111,293	503,831
Interest expense - affiliated												2,087	4,085	4,300
Other expenses												18,561	18,167	16,780
Total claims and expenses												20,648	22,252	21,080
INCOME (LOSS) BEFORE TAXES												1,009,461	89,041	482,751
NET INCOME (LOSS)												1,009,461	89,041	482,751
Unrealized appreciation (depreciation) ("URA(D)") on securities arising during the period												496,430	(255,656)	(64,348)
Reclassification adjustment for realized losses (gains) included in net income (loss)												(12,613)	27,496	(6,950)
Total URA(D) on securities arising during the period												483,817	(228,160)	(71,298)
Foreign currency translation adjustments												14,030	(76,816)	121,917
Benefit plan actuarial net gain (loss) for the period												(12,591)	(510)	1,027
Reclassification adjustment for amortization of net (gain) loss included in net income (loss)												5,453	5,021	5,477
Total benefit plan net gain (loss) for the period												(7,138)	4,511	6,504
Total other comprehensive income (loss), net of tax												490,709	(300,465)	57,123
COMPREHENSIVE INCOME (LOSS)												$ 1,500,170	$ (211,424)	$ 539,874