Income Taxes - Gross Unrecognized Tax Benefit (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at January 1	$ 9.2us-gaap_UnrecognizedTaxBenefits	$ 6.7us-gaap_UnrecognizedTaxBenefits
Increases in tax positions for current year	2.6	2.9
Settlements	0	0
Lapse in statute of limitations	(1.0)	(1.4)
Increases in tax positions for prior years	1.7	2.3
Decreases in tax positions for prior years		(1.3)
Gross unrecognized tax benefits at December 31	$ 12.5us-gaap_UnrecognizedTaxBenefits	$ 9.2us-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

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

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-Publisher FASB

-Name Accounting Standards Codification

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

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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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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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