Stock-Based Compensation Plans (Summary Of Stock Option Activity) (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Common Shares, Outstanding at beginning of the period (in shares)	1,551,734	1,618,426
Common Shares, Conversion of options of acquired company (in shares)		16,364
Common Shares, Granted (in shares)	562,166	502,517
Common Shares, Exercised (in shares)	(184,366)	(258,836)
Common Shares, Forfeited or canceled (in shares)	(86,039)	(277,150)
Common Shares, Outstanding at end of the period (in shares)	1,843,495	1,601,321
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Strike Price, Outstanding at beginning of period (usd per share)	$ 41.32	$ 43.00
Weighted Average Strike Price, Conversion of options of acquired company (usd per share)		21.18
Weighted Average Strike Price, Granted (usd per share)	41.04	44.36
Weighted Average Strike Price, Exercised (usd per share)	37.43	43.14
Weighted Average Strike Price, Forfeited or canceled (usd per share)	48.93	53.64
Weighted Average Strike Price, Outstanding at end of period (usd per share)	$ 41.27	$ 41.34
Stock Options, Exercisable (in shares)	813,666	715,101
Stock Options, Weighted Average Strike Price, Exercisable (usd per share)	$ 39.27	$ 37.52
Stock Options, Remaining Contractual Term, Outstanding, Years	4 years 9 months 18 days	4 years 8 months 12 days
Stock Options, Remaining Contractual Term, Exercisable, Years	3 years 6 months	3 years 2 months 12 days
Stock Options, Intrinsic Value, Outstanding	$ 26,363	$ 19,738
Stock Options, Intrinsic Value, Exercisable	$ 13,265	$ 11,376