Cash paid for amounts included in the measurement of lease liabilities.

No definition available.

Name:	rblx_CashPaidForAmountsIncludedInTheMeasurementOfLeaseLiabilities
Namespace Prefix:	rblx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessee, Operating Lease, Number Of Renewal Options

+ References

No definition available.

+ Details

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Namespace Prefix:	rblx_
Data Type:	xbrli:integerItemType
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

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

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918701-209980

+ Details

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

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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-Publisher FASB
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-SubTopic 20
-Section 50
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average discount rate for operating lease calculated at point in time.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Net cash outflow or inflow from monetary allowance granted by the landlord to a tenant to entice tenant to move into landlords building which will enable the tenant to prepare the leased premises for tenants occupancy.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

+ References

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-Publisher FASB
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LeaseContractualTermAxis=rblx_NewLeaseInSanMateoCaliforniaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Leases - Summary of Supplemental Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 option	Mar. 11, 2022 USD ($)
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	8 years 1 month 13 days
Weighted average discount rate	5.00%
Cash paid for amounts included in the measurement of lease liabilities	$ 47,546
Lease liabilities arising from obtaining new ROU assets	279,712
Leasehold incentive received	1,200
Operating leases, original commitment	$ 621,590
New Lease In San Mateo, California
Lessee, Lease, Description [Line Items]
Operating leases, original commitment			$ 125,500
Operating lease term		13 years
Number of renewal options \| option		2
Operating lease, renewal term		5 years