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

Debt Instrument, Convertible, Gross Amount of Equity Component

+ References

No definition available.

+ Details

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

- Definition

Debt Instrument, Convertible, Trading Price As A Percentage Of Stock Price And Debt Conversion Rate

+ References

No definition available.

+ Details

Name:	mdb_DebtInstrumentConvertibleTradingPriceAsAPercentageOfStockPriceAndDebtConversionRate
Namespace Prefix:	mdb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair Value, Cash Consideration, Effective Discount Rate

+ References

No definition available.

+ Details

Name:	mdb_FairValueCashConsiderationEffectiveDiscountRate
Namespace Prefix:	mdb_
Data Type:	num:percentItemType
Balance Type:	na
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

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 3: 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)(5))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- 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

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6036836-161870

Reference 2: 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 3: 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_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e31931-109318

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

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

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

- Details

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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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_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:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleSeniorNotesDue2026LiabilityComponentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mdb_ConvertibleSeniorNotesDue2026EquityComponentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_EquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Convertible Senior Notes - Additional Information (Details)		1 Months Ended	2 Months Ended	3 Months Ended	12 Months Ended
	Jan. 14, 2020 USD ($)	Jan. 31, 2020 USD ($) $ / shares	Jul. 31, 2018 USD ($) day $ / shares	Jan. 31, 2020 USD ($) $ / shares	Jan. 31, 2020 USD ($) day $ / shares	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)
Debt Instrument [Line Items]
Proceeds from borrowings on convertible senior notes, net of issuance costs		$ 1,130,000,000			$ 1,132,991,000	$ 291,145,000	$ 0
Effective discount rate	5.04%
Convertible debt, conversion ratio		4.7349	14.6738
Convertible debt, conversion ratio denominator			$ 1,000
Initial conversion price (in dollars per share) \| $ / shares		$ 211.20	$ 68.15	$ 211.20	$ 211.20
Consecutive threshold trading days \| day			30
Threshold percentage of stock price trigger			130.00%
Carrying amount of convertible debt equity component			$ 84,200,000
Debt issuance costs						$ 5,931,000
Fair value of convertible debt		$ 220,200,000		$ 220,200,000	$ 220,200,000
Net deferred tax liabilities		143,000		143,000	143,000
Minimum
Debt Instrument [Line Items]
Threshold trading days \| day			20
2026 Notes
Debt Instrument [Line Items]
Debt issuance costs		15,019,000		15,019,000	15,019,000
Fair value of convertible debt		1,200,000,000		$ 1,200,000,000	$ 1,200,000,000
2024 Notes Partial Repurchase
Debt Instrument [Line Items]
Debt issuance costs	$ 3,623,000
Redemption Period 1
Debt Instrument [Line Items]
Consecutive threshold trading days \| day			30		30
Threshold percentage of stock price trigger			130.00%	130.00%
Redemption Period 1 \| Minimum
Debt Instrument [Line Items]
Threshold trading days \| day			20		20
Redemption Period 2
Debt Instrument [Line Items]
Convertible debt, conversion ratio denominator			$ 1,000
Threshold trading days \| day			5
Consecutive threshold trading days \| day			5
Redemption Period 2 \| Maximum
Debt Instrument [Line Items]
Trading price as a percentage of stock price and debt conversion rate			98.00%
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		$ 100	$ 100
Percentage of principal amount redeemed			100.00%
Debt issuance costs			$ 8,800,000
Effective interest rate			7.03%
Convertible Debt \| 2026 Notes
Debt Instrument [Line Items]
Face amount of debt		$ 1,000,000,000.0		$ 1,000,000,000.0	$ 1,000,000,000.0
Interest rate		0.25%		0.25%	0.25%
Initial conversion price (in dollars per share) \| $ / shares		$ 211.20		$ 211.20	$ 211.20
Carrying amount of convertible debt equity component		$ 294,900,000		$ 294,900,000	$ 294,900,000
Debt issuance costs		$ 20,300,000		$ 20,300,000	$ 20,300,000
Effective interest rate		5.60%		5.60%	5.60%
Net deferred tax liabilities		$ 700,000		$ 700,000	$ 700,000
Convertible Debt \| Additional Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Face amount of debt		150,000,000.0		150,000,000.0	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	175,141,000
Debt issuance costs			$ 6,300,000
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
Debt issuance costs			2,500,000
Convertible Debt \| Convertible Senior Notes, Interest Component
Debt Instrument [Line Items]
Proceeds from borrowings on convertible senior notes, net of issuance costs	$ 200,000
Convertible Debt \| Convertible Senior Notes Due 2026, Liability Component
Debt Instrument [Line Items]
Debt issuance costs		15,100,000		15,100,000	15,100,000
Convertible Debt \| Convertible Senior Notes Due 2026, Equity Component
Debt Instrument [Line Items]
Debt issuance costs		5,200,000		5,200,000	5,200,000
Equity
Debt Instrument [Line Items]
Carrying amount of convertible debt equity component			$ 81,700,000
Equity \| Convertible Debt \| 2026 Notes
Debt Instrument [Line Items]
Carrying amount of convertible debt equity component		$ 289,000,000.0		$ 289,000,000.0	$ 289,000,000.0