Share-Based Payment Arrangements - Summary of Measurement of Fair Values - RSUs (Detail) - RSUs [member] - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Statement [Line Items]
Fair value at grant date (weighted average)	$ 1.96	$ 2.04
Expected dividend (weighted average)	0.00%	0.00%
Discount for lack of marketability	20.00%
Bottom of range [member]
Statement [Line Items]
Expected volatility	49.60%	46.60%
Risk free interest rate	0.13%	1.60%
Discount for lack of marketability		20.00%
Top of range [member]
Statement [Line Items]
Expected volatility	66.30%	49.60%
Risk free interest rate	1.60%	2.49%
Discount for lack of marketability		27.50%

Fair value at grant date (weighted average).

No definition available.

Name:	grab_FairValueAtGrantDateWeightedAverage
Namespace Prefix:	grab_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Share based compensation equity instruments other than options estimated discount rate due to lack of marketability

+ References

No definition available.

+ Details

Name:	grab_ShareBasedCompensationEquityInstrumentsOtherThanOptionsEstimatedDiscountRateDueToLackOfMarketability
Namespace Prefix:	grab_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Statement.

+ References

No definition available.

+ Details

Name:	grab_StatementLineItems
Namespace Prefix:	grab_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The expected volatility of the share price used to calculate the fair value of the share options granted. Expected volatility is a measure of the amount by which a price is expected to fluctuate during a period. The measure of volatility used in option pricing models is the annualised standard deviation of the continuously compounded rates of return on the share over a period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2021-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2021-en-r&anchor=para_47_a_i&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for share options granted is expressed, with a remaining term equal to the expected term of the option being valued (based on the option's remaining contractual life and taking into account the effects of expected early exercise). [Refer: Government [member]]

+ References

+ Details

Name:	ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of an expected dividend used to calculate the fair value of share options granted.

+ References

+ Details

Name:	ifrs-full_ExpectedDividendAsPercentageShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=grab_RestrictedShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: