Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reinsurance [Line Items]
Allowance for reinsurance receivables	$ 14,233	$ 12,836
Duration of Stop Loss Agreement			12 months
Subject loss reserves				$ 2,336,242
Amount of Transfer				1,000,000
Reinsurance coverage amount	1,318,338	1,278,115	$ 1,541,814
Bermuda Re [Member]
Reinsurance [Line Items]
Amount of Transfer				970,000
Adverse development coverage				$ 500,000
Reinsurance coverage amount	$ 131,341	100,084	$ 572,620
Bermuda Re [Member] | Catastrophe Reinsurance [Member]
Reinsurance [Line Items]
Reinsurance coverage amount		$ 100,000