Stock Option Exercises and Restricted Stock Vesting (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Employee Stock Options [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Proceeds from stock option exercises	$ 26.6	$ 20.6
Aggregate intrinsic value	61.9	21.6
Tax benefit realized upon exercise	$ 15.0	$ 7.9
Number of shares exercised	0.5	0.4
Restricted Stock [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Fair value of shares vested	$ 146.7	$ 106.8
Tax benefit realized upon vesting	$ 33.9	$ 33.7
Number of shares vested	0.9	0.9
Vesting of Performance Based Restricted Stock [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Fair value of shares vested	$ 23.0	$ 19.5
Tax benefit realized upon vesting	$ 5.5	$ 6.9
Number of shares vested	0.1	0.2

Amount of tax benefit from vesting of other than stock options granted under share-based compensation arrangement.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Section 50
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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of share options (or share units) exercised during the current period.

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