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Reinsurance (List of Direct, Assumed, and Ceded Reinsurance Amounts) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Premiums earned:
Net	$ 942,150	$ 834,439	$ 1,844,486	$ 1,646,722
Loss and loss expenses incurred:
Net	646,130	524,868	1,213,568	1,019,104
Direct Assumed and Ceded Reinsurance Amounts [Member]
Premiums written:
Direct	1,232,496	1,050,506	2,365,256	2,051,555
Assumed	5,577	8,552	10,971	13,866
Ceded	(153,166)	(128,317)	(291,552)	(244,882)
Net	1,084,907	930,741	2,084,675	1,820,539
Premiums earned:
Direct	1,073,498	955,651	2,105,726	1,887,027
Assumed	5,968	7,481	12,258	13,009
Ceded	(137,316)	(128,693)	(273,498)	(253,314)
Net	942,150	834,439	1,844,486	1,646,722
Loss and loss expenses incurred:
Direct	698,994	559,913	1,312,223	1,088,501
Assumed	5,678	5,125	10,933	9,403
Ceded	(58,542)	(40,170)	(109,588)	(78,800)
Net	$ 646,130	$ 524,868	$ 1,213,568	$ 1,019,104

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