Label	Element	Value
Frontier Markets Portfolio
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	ck0000836487_SupplementTextBlock	Prospectus Supplement January 31, 2019 Morgan Stanley Institutional Fund, Inc. Supplement dated January 31, 2019 to the Morgan Stanley Institutional Fund, Inc. Prospectuses dated April 30, 2018 Active International Allocation Portfolio Advantage Portfolio Asia Opportunity Portfolio Emerging Markets Breakout Nations Portfolio Emerging Markets Leaders Portfolio Emerging Markets Portfolio Emerging Markets Small Cap Portfolio Frontier Markets Portfolio Global Advantage Portfolio Global Concentrated Portfolio Global Core Portfolio Global Counterpoint Portfolio Global Franchise Portfolio Global Infrastructure Portfolio Global Opportunity Portfolio Global Real Estate Portfolio Global Sustain Portfolio Growth Portfolio International Advantage Portfolio International Equity Portfolio International Opportunity Portfolio International Real Estate Portfolio Small Company Growth Portfolio US Core Portfolio U.S. Real Estate Portfolio
Risk/Return [Heading]	rr_RiskReturnHeading	Frontier Markets Portfolio
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following is hereby added as the second paragraph of the section of each Prospectus entitled "Fund Summary—Fees and Expenses": Class I shares may be available on brokerage platforms of firms that have agreements with the Fund's principal underwriter permitting such firms to (i) offer Class I shares solely when acting as an agent for the investor and (ii) impose on an investor transacting in Class I shares through such platforms a commission and/or other forms of compensation to the broker. Shares of the Fund are available in other share classes that have different fees and expenses. Please retain this supplement for future reference.

This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown. The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 3
-Subsection instructions
-Paragraph 1
-Subparagraph b

Name:	rr_ExpenseNarrativeTextBlock
Namespace Prefix:	rr_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration