Financial Instruments And Investments (Sale Of Securities And The Related Effects On Pre-Tax Income ) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investment [Line Items]
Proceeds from sales of available-for-sale securities	$ 19,453	$ 26,618	$ 60,165	$ 63,776	$ 98,956	$ 124,732
Gross realized gains included in pre-tax income	2,446	4,515	6,687	8,330	10,736	12,467
Gross realized losses included in pre-tax income	(178)	(191)	(765)	(443)	(1,249)	(1,021)
Gross unrealized losses included in pre-tax income	(196)	0	(352)	0	(690)	0
Net gains (losses) in pre-tax income	2,072	4,324	5,570	7,887	8,797	11,446
Net unrealized holding gains (losses) included in accumulated other comprehensive income	4,313	(8,092)	9,293	(8,641)	15,028	(5,779)
Net (gains) losses reclassified out of accumulated other comprehensive income	(2,072)	(4,324)	(5,570)	(7,887)	(8,797)	(11,446)
Net gains (losses) in other comprehensive income	$ 2,241	$ (12,416)	$ 3,723	$ (16,528)	$ 6,231	$ (17,225)