2.4.0.82117100 - Disclosure - MARKETABLE SECURITIES (Notes)truefalsefalse1falsefalsefalseD2013Q2YTDhttp://www.sec.gov/CIK0001452575duration2013-01-01T00:00:002013-06-30T00:00:001true3us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse02false4mjn_MarketableSecuritiesDisclosureTextBlockmjn_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:3pt;font-weight:bold;">                        </font><font style="font-family:inherit;font-size:10pt;font-weight:bold;"> MARKETABLE SECURITIES</font></div><div style="line-height:120%;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"> </font></div><div style="line-height:120%;text-align:left;font-size:11pt;"><font style="font-family:inherit;font-size:10pt;">As of June 30, 2013, the Company held investments in equity securities of </font><font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;">$11.7 million</font><font style="font-family:inherit;font-size:10pt;"> classified as trading securities and included in </font><font style="font-family:inherit;font-size:10pt;font-style:italic;">prepaid expenses and other assets</font><font style="font-family:inherit;font-size:10pt;"> in the consolidated balance sheets. These investments </font><font style="font-family:inherit;font-size:11pt;">are carried</font><font style="font-family:inherit;font-size:10pt;"> at fair value based on quoted market prices and classified as Level 1 in the fair value hierarchy. Cost basis for the Company's equity securities is determined by the specific identification method. Realized and unrealized gains and losses on trading securities are included in </font><font style="font-family:inherit;font-size:10pt;font-style:italic;">other expenses/(income) - net</font><font style="font-family:inherit;font-size:10pt;"> in the Company's consolidated statements of earnings. </font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;"><br clear="none"/></font></div><div style="line-height:120%;text-align:left;font-size:10pt;"><font style="font-family:inherit;font-size:10pt;">The Company did not hold any investments classified as trading securities as of December 31, 2012. During the three months and six months ended June 30, 2013, the Company recognized losses on trading securities of </font><font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;">$0.3 million</font><font style="font-family:inherit;font-size:10pt;">. These investments in trading securities were sold in July 2013 in connection with the payment of the remaining balance of the note payable in connection with the Argentine Acquisition discussed in Note 15.</font></div></div>falsefalsefalsenonnum:textBlockItemTypenaMarketable Securities Disclosure [Text Block]No definition available.false0falseMARKETABLE SECURITIES (Notes)UnKnownUnKnownUnKnownUnKnowntruefalsefalseNoteshttp://www.meadjohnson.com/role/MarketableSecuritiesNotes12