It represents the principal amount of the long term borrowing under the credit facility.

No definition available.

Name:	g_LineOfCreditLongTermFacilityPrincipalAmount
Namespace Prefix:	g_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	g_MarginOverLiborForInterestRateOnLineOfCredit
Namespace Prefix:	g_
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Balance Type:	na
Period Type:	duration

- Definition

Maximum increase in downgrade of credit rating of notes to adjust interest rate payable.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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Balance Type:	na
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- 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.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

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- Definition

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

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- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase (decrease) of the credit facility.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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Period Type:	duration

- Details

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Long-Term Debt - Narrative (Detail) - USD ($)	1 Months Ended	9 Months Ended	12 Months Ended
Long-Term Debt - Narrative (Detail) - USD ($)	Aug. 31, 2018	Sep. 30, 2021	Dec. 31, 2020	Mar. 31, 2021	Nov. 30, 2019	Aug. 09, 2018	Aug. 08, 2018	Mar. 31, 2017
Debt Instrument [Line Items]
Margin over LIBOR (in percentage)	1.375%	1.375%	1.375%
Debt amount outstanding		$ 1,663,864,000	$ 1,340,908,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity						$ 500,000,000	$ 350,000,000
Term Loan Credit Facility
Debt Instrument [Line Items]
Debt amortization expense		801,000	1,150,000
Debt amount outstanding		568,699,000	593,850,000
Principal amount of term loan		8,500,000
2015 Facility
Debt Instrument [Line Items]
Margin over LIBOR (in percentage)	1.50%
Credit facility, base rate (in percentage)	0.50%
2015 Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 350,000,000
2015 Facility \| Term Loan Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	800,000,000
Outstanding term loan	550,814,000
Extinguished outstanding term loan	129,186,000
Change to outstanding principal of term loan	0
Amended 2015 Facility
Debt Instrument [Line Items]
Debt amortization expense	$ 2,029,000
Margin over LIBOR (in percentage)	1.375%
Credit facility, base rate (in percentage)	0.375%
Amended 2015 Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 500,000,000
Debt amortization expense	82,000
Amended 2015 Facility \| Term Loan Credit Facility
Debt Instrument [Line Items]
Outstanding term loan	680,000,000
Additional funding	$ 129,186,000
2017 Senior Notes \| Genpact Luxembourg S.r.l.
Debt Instrument [Line Items]
Debt amortization expense		264,000	658,000
Debt amount outstanding		$ 349,736,000	349,342,000
Principal amount of senior notes issued								$ 350,000,000
Interest rate on senior notes (in percentage)		3.70%						3.70%
Total debt issuance cost								$ 2,642,000
2019 Senior Notes \| Genpact Luxembourg S.r.l.
Debt Instrument [Line Items]
Debt amortization expense		$ 1,849,000	2,284,000
Debt amount outstanding		$ 398,152,000	$ 397,716,000
Principal amount of senior notes issued					$ 400,000,000
Interest rate on senior notes (in percentage)		3.375%			3.375%
Total debt issuance cost					$ 2,937,000
Debt instrument redemption price (in percentage)		100.00%
Debt repurchase price as percentage of aggregate principal value upon certain change of controls (in percentage)		101.00%
Maximum increase in downgrade of credit rating of notes to adjust interest rate payable (in percentage)		2.00%
2021 Senior Notes \| Genpact Luxembourg S.r.l.
Debt Instrument [Line Items]
Debt amortization expense		$ 2,723,000
Debt amount outstanding		$ 347,277,000
Principal amount of senior notes issued				$ 350,000,000
Interest rate on senior notes (in percentage)		1.75%		1.75%
Total debt issuance cost				$ 3,032,000