XML 74 R63.htm IDEA: XBRL DOCUMENT v3.25.3

Derivative financial instruments - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	May 31, 2024	Mar. 31, 2021
Treasury rate lock | 2021 Senior Notes
Derivative [Line Items]
Treasury lock on fair value edges, amount				$ 350,000
Derivative instrument, gain (loss) amortized	$ 85	$ 206
Treasury rate lock | 2024 Senior Notes
Derivative [Line Items]
Treasury lock on fair value edges, amount			$ 400,000
Derivative instrument, gain (loss) amortized	$ 292	$ 351
Maximum | Interest rate swaps
Derivative [Line Items]
Derivatives, maturity period	51 months
Maximum | Forward foreign exchange contracts
Derivative [Line Items]
Derivatives, maturity period	51 months

X

- Definition

Derivative Instrument Gain (Loss) Amortized

+ References

No definition available.

+ Details

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

X

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

+ Details

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

X

- Definition

Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeRemainingMaturity1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Net fair value of all derivative instruments designated as fair value hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B

+ Details

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

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_TreasuryLockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: