Collateralized Reinsurance And Trust Agreements (Narrative) (Details) $ in Thousands	Apr. 30, 2018 USD ($) item	Apr. 13, 2017 USD ($) item	Dec. 01, 2015 USD ($) item	Nov. 18, 2014 USD ($)	Apr. 24, 2014 USD ($) item	Jun. 30, 2019 USD ($)
Effects of Reinsurance [Line Items]
Amount on deposit in trust accounts						$ 644,803
Kilimanjaro Re Limited [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item		6	2		2
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item	4
Reinsurance coverage amount				$ 500,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member] | Southeastern United States [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount					$ 250,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member] | Southeast, Mid-Atlantic And Northeast United States And Puerto Rico [Member]
Effects of Reinsurance [Line Items]
Reinsurance contract expiration					Apr. 30, 2018
Reinsurance coverage amount					$ 200,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 1-2 [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item	2
Reinsurance Contracts	4 years
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreements 1- 3 [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item		3
Reinsurance Contracts		4 years
Reinsurance coverage amount	$ 200,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 1 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount		$ 225,000	$ 300,000
Catastrophe reinsurance bonds, funded amount	62,500
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 2 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount		400,000	325,000
Catastrophe reinsurance bonds, funded amount	$ 200,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 3-4 [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item	2
Reinsurance Contracts	5 years
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 3 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount	$ 62,500	$ 325,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreements 4 - 6 [Member]
Effects of Reinsurance [Line Items]
Number of collateralized reinsurance agreements | item		3
Reinsurance Contracts		5 years
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 4 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount		$ 50,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 5 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount		75,000
Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance Agreement 6 [Member]
Effects of Reinsurance [Line Items]
Reinsurance coverage amount		175,000
Series 2014-1 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount					$ 450,000
Catastrophe Reinsurance Bonds Redeemed Amount	450,000
Series 2014-2 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount				$ 500,000
Series 2015-1 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount			$ 625,000
Series 2017-1 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount		950,000
Series 2017-2 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount		$ 300,000
Series 2018-1 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount	262,500
Series 2018-2 Notes [Member] | Kilimanjaro Re Limited [Member] | Catastrophe Reinsurance [Member]
Effects of Reinsurance [Line Items]
Catastrophe reinsurance bonds, funded amount	$ 262,500