Former percent of common stock owned by the related party and certain of its affiliates.

No definition available.

Name:	mos_FormerRelatedPartyOwnershipPercentage
Namespace Prefix:	mos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of outstanding Mosaic shares held by Exchanging Cargill Stockholders immediately after the split-off

+ References

No definition available.

+ Details

Name:	mos_PercentageOfOutstandingSharesHeldByCargillAfterSplitOff
Namespace Prefix:	mos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting power held of Exchanging Cargill Stockholders immediately after the split-off

+ References

No definition available.

+ Details

Name:	mos_PercentageVotingPowerOfCargillAfterSplitOff
Namespace Prefix:	mos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Related Party Agreement, Prohibited Acts, Facilitating Participation In Company Management Or Operations By Other Third Party Shareholders, Ownership Interest After Split Off, Minimum

+ References

No definition available.

+ Details

Name:	mos_RelatedPartyAgreementProhibitedActsFacilitatingParticipationInCompanyManagementOrOperationsByOtherThirdPartyShareholdersOwnershipInterestAfterSplitOffMinimum
Namespace Prefix:	mos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Related Party Agreement, Prohibited Acts, Facilitating Purchase Of Company Stock By Other Third Party Shareholders, Ownership Interest After Split Off, Minimum

+ References

No definition available.

+ Details

Name:	mos_RelatedPartyAgreementProhibitedActsFacilitatingPurchaseOfCompanyStockByOtherThirdPartyShareholdersOwnershipInterestAfterSplitOffMinimum
Namespace Prefix:	mos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	mos_RemainingNumberOfSharesAuthorizedToBeConverted
Namespace Prefix:	mos_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate number of shares received by Cargill debt holders in the Split-off

+ References

No definition available.

+ Details

Name:	mos_SharesReceivedByCargillDebtHolders
Namespace Prefix:	mos_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate number of shares received by Exchanging Cargill Stockholders in the Split-off and not sold in the underwritten public secondary offering.

+ References

No definition available.

+ Details

Name:	mos_SharesReceivedByExchangingCargillStockholders
Namespace Prefix:	mos_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate number of shares received by Exchanging Cargill Stockholders in the Split-off

+ References

No definition available.

+ Details

Name:	mos_SharesReceivedByExchangingCargillStockholdersAfterSplitOff
Namespace Prefix:	mos_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate number of shares sold by certain Exchanging Cargill Stockholders and the Exchanging Cargill Debt Holders in an underwritten secondary public offering

+ References

No definition available.

+ Details

Name:	mos_SharesSoldSecondaryOffer
Namespace Prefix:	mos_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Face amount or stated value per share of common stock.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ConversionOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

Name:	us-gaap_ConversionOfStockSharesConverted1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_EquityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	mos_OutstaningStockOwnershipAxis=mos_ExchangingCargillStockholdersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=mos_CargillMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mos_CommonClassASeriesA1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mos_CommonClassASeriesA2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mos_CommonClassASeriesA4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mos_NoClassCommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Cargill Transaction (Details) (USD $)	0 Months Ended
Cargill Transaction (Details) (USD $)	May 25, 2011	Oct. 06, 2011	Nov. 26, 2013	Nov. 26, 2014	Sep. 29, 2011	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Former percentage ownership by Cargill and certain of its subsidiaries	64.00%
Shares Received By Exchanging Cargill Stockholders	178,300,000
Percentage Of Outstanding Shares Held By Cargill After Split Off	40.00%
Percentage of Cargill voting power after split off	82.00%
Mosaic shares received by Cargill debt holders	107,500,000mos_SharesReceivedByCargillDebtHolders
Shares sold in secondary offer	115,000,000mos_SharesSoldSecondaryOffer
Remaining shares of Mosaic stock received by Cargill stockholders and not sold in the formation offering	128,800,000
Exchanging Cargill Stockholders [Member]
Conversion of Stock [Line Items]
Number of shares remaining to be converted						17,176,046
Common Class A [Member]
Conversion of Stock [Line Items]
Common stock, par value (in usd per share)						0.01	$ 0.01
Common Class B [Member]
Conversion of Stock [Line Items]
Number of shares converted		113,000,000
Common stock, par value (in usd per share)						0.01	$ 0.01
Common Class A, Series A-1 [Member]
Conversion of Stock [Line Items]
Number of shares converted			42,900,000
Common Class A, Series A-1 [Member] \| MAC Trusts [Member]
Conversion of Stock [Line Items]
Number of shares converted			21,647,007
Common Class A, Series A-2 [Member] \| Exchanging Cargill Stockholders [Member]
Conversion of Stock [Line Items]
Number of shares converted				17,176,068
Common Class A, Series A-4 [Member] \| MAC Trusts [Member]
Conversion of Stock [Line Items]
Number of shares converted					20,700,000
No Class Common Stock [Member]
Conversion of Stock [Line Items]
Common stock, par value (in usd per share)			0.01			0.01	$ 0.01
Cargill [Member]
Conversion of Stock [Line Items]
Prohibited ownership percentage to benefit from facilitation to acquire our stock from Cargill transaction	10.00%
Prohibited ownership percentage by management to benefit from facilitation to acquire our stock from Cargill transaction	5.00%