Stock-Based Compensation - Options Outstanding and Exercisable (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, aggregate intrinsic value	$ 225.9
Options exercisable, weighted-average remaining contractual life	4 years 10 months 24 days
Options exercisable, aggregate intrinsic value	$ 196.0

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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