Share Plans - Stock Option Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Shares
Beginning balance | shares	5.7
Granted | shares	0.7
Exercised | shares	(0.7)
Forfeited | shares	(0.1)
Ending balance | shares	5.6
Options exercisable | shares	4.4
Options expected to vest at end of period | shares	1.2
Weighted Average Exercise Price
Beginning balance (USD per share) | $ / shares	$ 39.08
Granted (USD per share) | $ / shares	65.30
Exercised (USD per share) | $ / shares	35.27
Forfeited (USD per share) | $ / shares	64.52
Ending Balance (USD per share) | $ / shares	42.55
Options exercisable at end of period (USD per share) | $ / shares	35.93
Options expected to vest at end of period (USD per share) | $ / shares	$ 65.24
Weighted Average Remaining Contractual Life
Ending balance	4 years 9 months 18 days
Options exercisable at end of period	3 years 10 months 24 days
Options expected to vest at end of period	8 years 1 month 6 days
Aggregate Intrinsic value
Balance at end of period | $	$ 61.7
Options exercisable at end of period | $	61.7
Options expected to vest at end of period | $	$ 0.0