Financial Instruments Carried at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivatives, assets	$ 41.8us-gaap_DerivativeAssets	$ 20.5us-gaap_DerivativeAssets
Total, assets	239.5us-gaap_AssetsFairValueDisclosure	232.8us-gaap_AssetsFairValueDisclosure
Derivatives, liabilities	2.1us-gaap_DerivativeLiabilities	1.7us-gaap_DerivativeLiabilities
Contingent consideration arising from acquisitions, liabilities	2.1	17.5
Total, liabilities	4.2us-gaap_LiabilitiesFairValueDisclosure	19.2us-gaap_LiabilitiesFairValueDisclosure
money market	149.7us-gaap_MoneyMarketFundsAtCarryingValue	212.3us-gaap_MoneyMarketFundsAtCarryingValue
fixed maturity and open ended mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed Maturity Mutual Funds and Open Ended Mutual Funds	48.0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivatives, assets	41.8	20.5
Total, assets	41.8	20.5
Derivatives, liabilities	2.1	1.7
Contingent consideration arising from acquisitions, liabilities	0	0
Total, liabilities	2.1	1.7
Fixed Maturity Mutual Funds and Open Ended Mutual Funds	0
money market	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivatives, assets
Total, assets
Derivatives, liabilities	0	0
Contingent consideration arising from acquisitions, liabilities	2.1	17.5
Total, liabilities	2.1	17.5
Fixed Maturity Mutual Funds and Open Ended Mutual Funds	0
money market	0	0
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivatives, assets
Total, assets	197.7	212.3
Derivatives, liabilities	0	0
Contingent consideration arising from acquisitions, liabilities	0	0
Total, liabilities
money market	149.7	212.3
Level 1 \| fixed maturity and open ended mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed Maturity Mutual Funds and Open Ended Mutual Funds	$ 48.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

-Publisher FASB

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount of liability recognized arising from contingent consideration in a business combination.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

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