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, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Investment [Line Items]
Proceeds from sales of available-for-sale securities	$ 24,078	$ 24,642	$ 102,003	$ 104,126
Gross realized gains included in pre-tax income	1,832	3,782	10,429	8,626
Gross realized losses included in pre-tax income	(288)	(37)	(1,178)	(396)
Gross unrealized losses included in pre-tax income	(156)	0	(494)	0
Net gains (losses) in pre-tax income	1,388	3,745	8,757	8,230
Net unrealized holding gains (losses) included in accumulated other comprehensive income	2,190	1,014	(1,730)	10,843
Net (gains) losses reclassified out of accumulated other comprehensive income	(1,388)	(3,745)	(8,757)	(8,230)
Net gains (losses) in other comprehensive income	$ 802	$ (2,731)	$ (10,487)	$ 2,613