Stock Benefit Plan (Summary Of Stock Option Activity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Options, Beginning Balance	3,169,105
Options outstanding, Weighted Average Exercise Price Per Option, Beginning Balance	$ 44.98
Granted, Number of Options	166,810
Granted, Weighted Average Exercise Price Per Option	$ 62.09
Exercised, Number of Options	(540,667)
Exercised, Weighted Average Exercise Price Per Option	$ 44.10
Cancelled, Number of Options	(20,876)
Cancelled, Weighted Average Exercise Price Per Option	$ 50.10
Options outstanding, Number of Options, Ending Balance	2,774,372
Options outstanding, Weighted Average Exercise Price Per Option, Ending Balance	$ 46.14
Options outstanding, Weighted Average Remaining Contractual Term in Years	5.6
Options outstanding, Aggregate Intrinsic Value	$ 31,711
Options Exercisable, Number of Options	1,695,451
Options Exercisable, Weighted Average Exercise Price Per Option	$ 45.28
Options Exercisable, Weighted Average Remaining Contractual Term in Years	4.4
Options Exercisable, Aggregate Intrinsic Value	$ 20,837
Unvested Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Number of Options, Beginning Balance	1,391,013
Options outstanding, Weighted Average Exercise Price Per Option, Beginning Balance	$ 45.75
Granted, Number of Options	166,810
Granted, Weighted Average Exercise Price Per Option	$ 62.09
Vested, Number of Options	(458,026)
Vested, Weighted Average Exercise Price Per Option	$ 47.43
Cancelled, Number of Options	(20,876)
Cancelled, Weighted Average Exercise Price Per Option	$ 50.10
Options outstanding, Number of Options, Ending Balance	1,078,921
Options outstanding, Weighted Average Exercise Price Per Option, Ending Balance	$ 47.48