Summary of Option Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Shares
Shares, Outstanding, Beginning Balance | shares	6.0
Shares, Granted | shares	0.3
Shares, Exercised | shares	(1.5)
Shares, Outstanding, Ending Balance | shares	4.8
Shares, Vested and expected to vest | shares	4.7
Shares, Exercisable | shares	3.9
Weighted Average Exercise Price
Weighted Average Exercise Price Per Share, Beginning Balance | $ / shares	$ 46
Weighted Average Exercise Price Per Share, Granted | $ / shares	98.08
Weighted Average Exercise Price Per Share, Exercised | $ / shares	54.89
Weighted Average Exercise Price Per Share, Ending Balance | $ / shares	46.47
Weighted Average Exercise Price Per Share, Vested and expected to vest | $ / shares	45.9
Weighted Average Exercise Price Per Share, Exercisable | $ / shares	$ 40.79
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term, Outstanding	4 years 1 month 6 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	4 years
Weighted Average Remaining Contractual Term	3 years 2 months 12 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding | $	$ 256.9
Aggregate Intrinsic Value, Vested and expected to vest | $	254.9
Aggregate Intrinsic Value, Exercisable | $	$ 231.2