Name:	g_FundBasedNonFundBasedCreditFacilityLimit
Namespace Prefix:	g_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Utilized amount of borrowed credit facility as of the balance sheet date.

No definition available.

Name:	g_LineOfCreditFacilityAmountUtilized
Namespace Prefix:	g_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

This element represents the margin to be added to LIBOR to arrive at the interest rate to be paid on the credit facility.

No definition available.

Name:	g_MarginOverLiborForInterestRateOnLineOfCredit
Namespace Prefix:	g_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Term SOFR Adjustment

No definition available.

Name:	g_TermSOFRAdjustment
Namespace Prefix:	g_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

It represents the fee, expressed as a percentage of the unutilized amount of the line of credit facility.

No definition available.

Name:	g_UnutilizedAmountOfLineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	g_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

This element represents the utilization of credit facility for non-fund based usage for short term in the form of overdraft, letter of credit, guarantees, short term loans excluding forward hedging.

No definition available.

Name:	g_UtilizationOfCreditFacilityForNonFundBasedUsage
Namespace Prefix:	g_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

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

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
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-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 852
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
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-Name Accounting Standards Codification
-Section S99
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Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Name:	us-gaap_DebtInstrumentAxis=g_A2022CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_VariableRateAxis=g_BaseRatePlusApplicableMarginMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: