Financial Instruments And Investments (Sale Of Securities And The Related Effects On Pre-Tax Income ) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Investment [Line Items]
Proceeds from sales or maturities of available-for-sale securities	$ 15,771	$ 11,757	$ 29,969	$ 82,739
Gross realized gains included in pre-tax income	58	9	66	9,195
Gross realized losses included in pre-tax income	(887)	(527)	(1,822)	(1,278)
Net gains (losses) included in pre-tax income	$ (829)	$ (518)	$ (1,756)	$ 7,917