Debt Instrument, Convertible, Conversion Ratio, Denominator

No definition available.

Name:	mdb_DebtInstrumentConvertibleConversionRatioDenominator
Namespace Prefix:	mdb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

No definition available.

+ Details

Name:	us-gaap_ConvertibleDebtFairValueDisclosures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdTradingDays
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleNotesDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleNotesDue2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_AdditionalConvertibleSeniorNotesDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_A2024NotesPartialRepurchaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleSeniorNotesLiabilityComponentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleSeniorNotesEquityComponentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleSeniorNotesInterestComponentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Convertible Senior Notes - Additional Information (Details)		1 Months Ended	2 Months Ended	3 Months Ended
	Jan. 14, 2020 USD ($)	Jan. 31, 2020 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2020 USD ($) day	Jun. 30, 2018 USD ($)
2026 Notes
Debt Instrument [Line Items]
Fair value of convertible debt				$ 1,200,000,000
2024 Notes
Debt Instrument [Line Items]
Fair value of convertible debt				$ 193,500,000
Redemption Period 1
Debt Instrument [Line Items]
Threshold percentage of stock price trigger				130.00%
Consecutive threshold trading days \| day				30
Redemption Period 1 \| Minimum
Debt Instrument [Line Items]
Threshold trading days \| day				20
Convertible Debt
Debt Instrument [Line Items]
Face amount of debt	$ 90,000,000.0		$ 50,000,000.0		$ 250,000,000.0
Interest rate			0.75%		0.75%
Proceeds from borrowings on convertible senior notes, net of issuance costs	479,200,000		$ 291,100,000
Convertible debt, conversion ratio denominator				$ 100
Convertible Debt \| 2026 Notes
Debt Instrument [Line Items]
Face amount of debt		$ 1,000,000,000.0
Interest rate		0.25%
Proceeds from borrowings on convertible senior notes, net of issuance costs		$ 1,130,000,000
Convertible Debt \| Additional Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Face amount of debt		$ 150,000,000.0
Convertible Debt \| 2024 Notes Partial Repurchase
Debt Instrument [Line Items]
Face amount of debt	210,000,000.0
Convertible Debt \| Convertible Senior Notes, Liability Component
Debt Instrument [Line Items]
Proceeds from borrowings on convertible senior notes, net of issuance costs	175,100,000
Convertible Debt \| Convertible Senior Notes, Equity Component
Debt Instrument [Line Items]
Proceeds from borrowings on convertible senior notes, net of issuance costs	303,900,000
Convertible Debt \| Convertible Senior Notes, Interest Component
Debt Instrument [Line Items]
Proceeds from borrowings on convertible senior notes, net of issuance costs	$ 200,000