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, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Financial Instruments And Investments [Abstract]
Proceeds from sales of available-for-sale securities	$ 19,579	$ 14,231	$ 88,274	$ 56,383
Gross realized gains included in pre-tax income	389	264	1,604	897
Gross realized losses included in pre-tax income	(176)	(59)	(838)	(520)
Gross unrealized losses included in pre-tax income	0	0	(2,116)	(263)
Net gains (losses) in pre-tax income	213	205	(1,350)	114
Net unrealized holding gains (losses) included in accumulated other comprehensive income	8,158	2,173	7,555	6,415
Net gains (losses) reclassified out of accumulated other comprehensive income	(213)	(205)	1,350	(114)
Net gains in other comprehensive income	$ 7,945	$ 1,968	$ 8,905	$ 6,301