Employee Benefit Plans (Summary Of Activity In Corporation's Active Stock Plans) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Beginning Balance, Shares Available for Grant	2,759,347	3,445,507	963,825
Beginning Balance, Director Deferred Stock Units Outstanding	16,515	12,688	5,450
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 12.94	$ 14.43
Shares Available for Grant, Shares authorized - 2005 Plan			3,310,725
Granted, Shares Available for Grant	(868,267)	(814,910)	(849,818)
Granted, Director Deferred Stock Units Outstanding	5,577	5,030	7,238
Stock options exercised, Number of Shares	(148,203)	(820,853)	(426,625)
Deferred stock unit conversions, Director Deferred Stock Units outstanding		(1,203)
Forfeited, Shares Available for Grant	73,250	150,500	24,250
Cancelled/expired, Shares Available for Grant	(875)	(21,750)	(3,475)
Ending Balance, Shares Available for Grant	1,963,455	2,759,347	3,445,507
Ending Balance, Director Deferred Stock Units Outstanding	22,092	16,515	12,688
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 9.78	$ 12.94	$ 14.43
Options Outstanding [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning Balance, Number of Shares	4,383,885	4,600,455	4,272,050
Beginning Balance, Weighted-Average Exercise Price	$ 52.08	$ 51.18	$ 49.98
Granted, Number of Shares	806,390	753,580	786,280
Granted, Weighted-Average Exercise Price	$ 48.02	$ 52.51	$ 50.64
Stock options exercised, Shares Available for Grant	806,390	753,580	786,280
Stock options exercised, Number of Shares	(148,203)	(819,650)	(426,625)
Stock options exercised, Weighted-Average Exercise Price	$ 50.18	$ 47.34	$ 38.03
Forfeited, Number of Shares	(73,250)	(150,500)	(24,250)
Forfeited, Weighted-Average Exercise Price	$ 51.43	$ 52.49	$ 52.71
Cancelled/expired, Number of Shares			(7,000)
Cancelled/expired, Weighted-Average Exercise Price			$ 52.09
Ending Balance, Number of Shares	4,968,822	4,383,885	4,600,455
Ending Balance, Weighted-Average Exercise Price	$ 51.49	$ 52.08	$ 51.18
Non-Vested Stock Awards/Stock Units Outstanding [Member]
Defined Benefit Plan Disclosure [Line Items]
Beginning Balance, Number of Shares	227,550	233,200	229,000
Beginning Balance, Weighted-Average Grant-Date Fair Value	$ 51.10	$ 52.27	$ 52.16
Granted, Number of Shares	56,300	56,300	56,300
Granted, Weighted-Average Grant-Date Fair Value	$ 48.00	$ 52.46	$ 50.64
Stock options exercised, Shares Available for Grant	56,300	56,300	56,300
Stock awards vested, Number of Shares	(114,320)	(61,950)	(52,100)
Stock awards vested, Weighted-Average Grant-Date Fair Value	$ 50.19	$ 56.73	$ 50.01
Ending Balance, Number of Shares	169,530	227,550	233,200
Ending Balance, Weighted-Average Grant-Date Fair Value	$ 50.33	$ 51.10	$ 52.27