Collateralized Reinsurance And Trust Agreements (Premiums And Losses Ceded By The Company To Affiliate) (Details) - Mt. Logan Re Segregated Accounts [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Effects of Reinsurance [Line Items]
Ceded written premiums	$ 80,028	$ 81,036
Ceded earned premiums	56,732	61,409
Ceded losses and LAE	45,613	21,069
Assumed written premiums	2,309	3,043
Assumed earned premiums	2,309	3,043
Assumed losses and LAE

Amount of written premiums ceded to other entities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Name:	us-gaap_CededPremiumsWritten
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration