Financial Instruments And Investments (Sale Of Securities And The Related Effects On Pre-Tax Income ) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Financial Instruments And Investments [Abstract]
Proceeds from sales of available-for-sale securities	$ 10,907	$ 19,579	$ 89,870	$ 88,274
Gross realized gains included in pre-tax income	39	389	1,128	1,604
Gross realized losses included in pre-tax income	(197)	(176)	(2,062)	(838)
Unrealized losses included In pre-tax income	0	0	(479)	(2,116)
Net gains (losses) in pre-tax income	(158)	213	(1,413)	(1,350)
Net unrealized holding gains (losses) included in accumulated other comprehensive income	6,793	8,158	8,562	7,555
Net gains (losses) in other comprehensive income	$ 6,951	$ 7,945	$ 9,975	$ 8,905