Related-Party Transactions (Premiums And Losses Ceded By The Company To Affiliate) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Mt Logan Re [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums	$ 97,649	$ 74,215	$ 225,592	$ 211,429
Ceded earned premiums	86,049	62,543	212,153	202,810
Ceded losses and LAE	97,070	68,879	191,677	143,179
Bermuda Re [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums	78,330	32,255	224,131	96,353
Ceded earned premiums	77,078	32,278	221,754	95,215
Ceded losses and LAE	12,355	12,605	3,241	4,263
Assumed written premiums	4,820		4,820
Assumed earned premiums	3,676	62	3,799	186
Assumed losses and LAE	(199)	62	(134)	115
Ireland Re [Member]
Effects of Reinsurance [Line Items]
Assumed written premiums	7,092		12,993
Assumed earned premiums	7,092		12,018
Assumed losses and LAE	62,472		62,472
Ireland Insurance [Member]
Effects of Reinsurance [Line Items]
Assumed written premiums	3,619	1,217	6,409	3,723
Assumed earned premiums	1,724	788	4,237	2,569
Assumed losses and LAE	1,134	704	2,139	1,625
Lloyd S Syndicate [Member]
Effects of Reinsurance [Line Items]
Assumed written premiums	56	(1,743)	728	(4,144)
Assumed earned premiums	81	(1,743)	722	(3,926)
Assumed losses and LAE	(473)	293	(259)	(331)
Everest International and Canada [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums
Ceded earned premiums
Ceded losses and LAE				16
Assumed written premiums				1
Assumed earned premiums				(7)
Assumed losses and LAE	$ 46	$ (1,709)	$ 112	$ (1,059)