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Reinsurance (List of Direct, Assumed, and Ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Premiums earned:
Net	$ 853,879	$ 767,247	$ 2,500,601	$ 2,232,725
Loss and loss expenses incurred:
Net	547,826	505,269	1,566,930	1,340,293
Direct Assumed and Ceded Reinsurance Amounts [Member]
Premiums written:
Direct	1,037,612	932,752	3,089,166	2,796,296
Assumed	9,531	7,136	23,398	17,541
Ceded	(143,749)	(126,982)	(388,631)	(369,548)
Net	903,394	812,906	2,723,933	2,444,289
Premiums earned:
Direct	984,981	877,620	2,872,008	2,568,445
Assumed	8,514	6,304	21,523	16,391
Ceded	(139,616)	(116,677)	(392,930)	(352,111)
Net	853,879	767,247	2,500,601	2,232,725
Loss and loss expenses incurred:
Direct	732,568	655,483	1,821,069	1,557,063
Assumed	6,443	4,143	15,846	10,807
Ceded	(191,185)	(154,357)	(269,985)	(227,577)
Net	$ 547,826	$ 505,269	$ 1,566,930	$ 1,340,293

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