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, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Investment [Line Items]
Proceeds from sales or maturities of available-for-sale securities	$ 26,055	$ 24,078	$ 93,245	$ 102,003
Gross realized gains included in pre-tax income	2,587	1,832	9,968	10,429
Gross realized losses included in pre-tax income	(396)	(288)	(1,329)	(1,178)
Gross unrealized losses included in pre-tax income	0	(156)	(196)	(494)
Net gains included in pre-tax income	2,191	1,388	8,443	8,757
Net unrealized holding gains (losses) included in accumulated other comprehensive income	7,721	2,190	13,975	(1,730)
Net gains reclassified from accumulated other comprehensive income	(2,191)	(1,388)	(8,443)	(8,757)
Net gains (losses) in other comprehensive income	$ 5,530	$ 802	$ 5,532	$ (10,487)