Consolidated Statements Of Operations And Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUES:
Premiums earned	$ 2,205,811	$ 1,905,619	$ 6,285,030	$ 5,455,615
Net investment income	234,233	181,058	420,116	501,062
Net realized capital gains (losses):
Credit allowances on fixed maturity securities	6,196		(19,641)
Other-than-temporary impairments on fixed maturity securities		(7,314)		(15,404)
Other net realized capital gains (losses)	104,007	(5,629)	103,904	124,965
Total net realized capital gains (losses)	110,203	(12,943)	84,263	109,561
Net derivative gain (loss)	2,456	(189)	(1,048)	3,395
Other income (expense)	57,481	(31,025)	48,354	(52,550)
Total revenues	2,610,184	2,042,520	6,836,715	6,017,083
CLAIMS AND EXPENSES:
Incurred losses and loss adjustment expenses	1,736,210	1,371,924	4,574,066	3,515,104
Commission, brokerage, taxes and fees	445,332	443,076	1,360,170	1,253,500
Other underwriting expenses	138,875	118,158	385,865	321,976
Corporate expenses	10,618	8,435	29,184	22,622
Interest, fees and bond issue cost amortization expense	6,641	7,907	21,477	23,972
Total claims and expenses	2,337,676	1,949,500	6,370,762	5,137,174
INCOME (LOSS) BEFORE TAXES	272,508	93,020	465,953	879,909
Income tax expense (benefit)	29,451	(11,378)	15,404	88,092
NET INCOME (LOSS)	243,057	104,398	450,549	791,817
Other comprehensive income (loss), net of tax :
Unrealized appreciation (depreciation) ("URA(D)") on securities arising during the period	63,480	93,765	335,835	524,589
Reclassification adjustment for realized losses (gains) included in net income (loss)	(11,453)	(529)	12,689	(4,220)
Total URA(D) on securities arising during the period	52,027	93,236	348,524	520,369
Foreign currency translation adjustments	60,628	(3,426)	30,390	(15,206)
Reclassification adjustment for amortization of net (gain) loss included in net income (loss)	1,806	1,363	4,532	3,665
Total benefit plan net gain (loss) for the period	1,806	1,363	4,532	3,665
Total other comprehensive income (loss), net of tax	114,461	91,173	383,446	508,828
COMPREHENSIVE INCOME (LOSS)	$ 357,518	$ 195,571	$ 833,995	$ 1,300,645
EARNINGS PER COMMON SHARE:
Basic	$ 6.08	$ 2.56	$ 11.20	$ 19.44
Diluted	$ 6.07	$ 2.56	$ 11.18	$ 19.38