OTHER EXPENSES-NET (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrual related to the China investigation	$ 12.0	$ 0
Foreign exchange (gains)/losses-net	(2.8)	6.4
Severance and Other Costs	2.6mjn_SeveranceAndOtherCosts	0mjn_SeveranceAndOtherCosts
Gain on Sale of Investments	0us-gaap_GainOnSaleOfInvestments	(4.0)us-gaap_GainOnSaleOfInvestments
Other Nonoperating Income (Expense)	0.4us-gaap_OtherNonoperatingIncomeExpense	(1.7)us-gaap_OtherNonoperatingIncomeExpense
Other Expenses—net	12.2mjn_OtherExpensesincomenet	0.7mjn_OtherExpensesincomenet
VENEZUELA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Foreign exchange (gains)/losses-net	1.8	2.1
Change in Accounting Method Accounted for as Change in Estimate [Member] \| VENEZUELA
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Foreign exchange (gains)/losses-net		$ 6.1

Accrual related to the China investigation

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- Definition

Other Expenses/(Income)—net [Abstract] operating and non-operating

+ References

No definition available.

+ Details

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- Definition

The charge against earnings in the period for known and estimated costs of termination benefits provided to current employees that are involuntarily terminated under a benefit arrangement associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, excluding costs or losses pertaining to an entity newly acquired in a business combination or a discontinued operation as defined by generally accepted accounting principles, costs associated with one-time termination benefits and other costs not otherwise stated.

+ References

No definition available.

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- Definition

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30690-110894

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 20

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30700-110894

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- Definition

The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

+ References

No definition available.

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- Definition

The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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