Related-Party Transactions (Premiums And Losses Ceded By The Company To Affiliate) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Mt. Logan Re Segregated Accounts [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums	$ 95,350	$ 63,223
Ceded earned premiums	79,855	44,822
Ceded losses and LAE	37,465	34,623
Assumed written premiums
Assumed earned premiums
Assumed losses and LAE
Bermuda Re [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums	30,500	51,473
Ceded earned premiums	30,500	52,524
Ceded losses and LAE	(22,159)	11,733
Everest International [Member]
Effects of Reinsurance [Line Items]
Ceded written premiums
Ceded earned premiums
Ceded losses and LAE	22	10
Everest Canada [Member]
Effects of Reinsurance [Line Items]
Assumed written premiums	236
Assumed earned premiums	39
Assumed losses and LAE	1,598	(1,601)
Lloyd's Syndicate [Member]
Effects of Reinsurance [Line Items]
Assumed written premiums	(3,031)	(9,209)
Assumed earned premiums	(2,822)	(18,827)
Assumed losses and LAE	$ 814	$ (7,918)