Shareholders Equity and Stock Options (Deferred Stock Units) (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance		$ 37.54	$ 36.63	$ 38.40	$ 37.54
Options granted	$ 41.27	$ 41.27	$ 46.29	$ 24.26
Options exercised	$ 42.97	$ 42.97	$ 33.61	$ 31.33
Ending Balance	$ 40.58	$ 40.58	$ 37.54	$ 36.63	$ 37.54
Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested awards outstanding, beginning balance		27,350	30,250	41,200
Beginning Balance		$ 28.80	$ 28.98	$ 24.76
Awards granted		17,600	16,650	25,100
Options granted		$ 38.64	$ 45.95	$ 29.85
Stock issued		(14,800)	(19,550)	(36,050)
Options exercised		$ 45.95	$ 43.69	$ 24.76
Non-vested awards outstanding, ending balance	30,150	30,150	27,350	30,250
Ending Balance	$ 26.13	$ 26.13	$ 28.80	$ 28.98