Income Taxes - Reconciliations of Gross Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 60.8us-gaap_UnrecognizedTaxBenefits	$ 53.4us-gaap_UnrecognizedTaxBenefits	$ 26.5us-gaap_UnrecognizedTaxBenefits
Gross increases for tax positions in prior periods	2.3	12.2	2.2
Gross decreases for tax positions in prior periods	(0.5)	(0.6)	(0.6)
Gross increases based on tax positions related to the current year	1.8	2.7	13.6
Gross decreases related to settlements with taxing authorities	(0.1)	(5.1)	(13.2)
Reductions due to statute expiration	(1.2)	(1.8)	(0.4)
Unrecognized Tax Benefits, Decrease Resulting from Foreign Currency Translation	(1.0)	0	0
Gross increases due to acquisitions	0	0	25.3
Ending balance	$ 62.1us-gaap_UnrecognizedTaxBenefits	$ 60.8us-gaap_UnrecognizedTaxBenefits	$ 53.4us-gaap_UnrecognizedTaxBenefits

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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Amount of decrease in unrecognized tax benefits resulting from foreign currency translation.

+ References

No definition available.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15A

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of increase in unrecognized tax benefits resulting from acquisitions.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

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