SCHEDULE IV - SUPPLEMENTARY REINSURANCE INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Supplementary Insurance Information [Line Items]
GROSS AMOUNT	$ 4,405,452	$ 3,610,201	$ 3,275,997
CEDED TO OTHER COMPANIES	2,759,360	2,490,529	2,409,243
ASSUMED FROM OTHER COMPANIES	3,280,532	3,216,737	3,622,861
NET AMOUNT	$ 4,926,624	$ 4,336,409	$ 4,489,615
PERCENTAGE OF AMOUNT ASSUMED TO NET	66.60%	74.20%	80.70%
Property and Casualty
Supplementary Insurance Information [Line Items]
GROSS AMOUNT	$ 4,233,758	$ 3,455,690	$ 3,134,462
CEDED TO OTHER COMPANIES	2,700,693	2,446,890	2,311,001
ASSUMED FROM OTHER COMPANIES	2,874,687	2,840,834	3,187,623
NET AMOUNT	$ 4,407,752	$ 3,849,634	$ 4,011,084
PERCENTAGE OF AMOUNT ASSUMED TO NET	65.20%	73.80%	79.50%
Accident and health
Supplementary Insurance Information [Line Items]
GROSS AMOUNT	$ 171,694	$ 154,511	$ 141,535
CEDED TO OTHER COMPANIES	58,667	43,639	98,242
ASSUMED FROM OTHER COMPANIES	405,845	375,903	435,238
NET AMOUNT	$ 518,872	$ 486,775	$ 478,531
PERCENTAGE OF AMOUNT ASSUMED TO NET	78.20%	77.20%	91.00%