Investments (Gains And Losses Due To Changes In Fair Value Of Investments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gains and losses due to changes in fair value of investments	$ 28,065	$ 17,608	$ 20,275	$ 21,857	$ (67,332)	$ (21,132)	$ 37,127	$ 18,531	$ 87,927	$ (32,805)	$ (61,731)
Fixed Maturity Securities [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gains and losses due to changes in fair value of investments									50,403	(56,584)	(39,304)
Equity Securities [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gains and losses due to changes in fair value of investments									37,486	23,722	(22,988)
Short-term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gains and losses due to changes in fair value of investments									$ 38	$ 57	$ 561