Share Plans - Stock Option Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Shares
Beginning balance | shares	5.6
Granted | shares	1.3
Exercised | shares	(1.0)
Forfeited | shares	(0.1)
Expired | shares	0.1
Ending balance | shares	5.7
Options exercisable | shares	3.9
Options expected to vest at end of period | shares	1.8
Weighted Average Exercise Price
Beginning balance (USD per share) | $ / shares	$ 42.55
Granted (USD per share) | $ / shares	47.99
Exercised (USD per share) | $ / shares	32.38
Forfeited (USD per share) | $ / shares	59.24
Expired (USD per share) | $ / shares	30.18
Ending Balance (USD per share) | $ / shares	45.72
Options exercisable at end of period (USD per share) | $ / shares	41.05
Options expected to vest at end of period (USD per share) | $ / shares	$ 56.04
Weighted Average Remaining Contractual Life
Ending balance	5 years 3 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 7 months 6 days
Aggregate Intrinsic value
Balance at end of period | $	$ 74.9
Options exercisable at end of period | $	67.3
Options expected to vest at end of period | $	$ 7.6