Name:	giii_DebtInstrumentMaximumBorrowingCapacity
Namespace Prefix:	giii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents effect of change on interest expenses.

+ References

No definition available.

+ Details

Name:	giii_EffectOfChangeOnInterestExpenses
Namespace Prefix:	giii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents leverage ratio description.

+ References

No definition available.

+ Details

Name:	giii_LeverageRatioDescription
Namespace Prefix:	giii_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents leverage ratio description.

+ References

No definition available.

+ Details

Name:	giii_LeverageRatioDescriptionThree
Namespace Prefix:	giii_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents leverage ratio description.

+ References

No definition available.

+ Details

Name:	giii_LeverageRatioDescriptionTwo
Namespace Prefix:	giii_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents percentage prepayment of excess cash flow as agreed.

+ References

No definition available.

+ Details

Name:	giii_PercentagePrepaymentOfExcessCashFlow
Namespace Prefix:	giii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents percentage prepayment of excess Cash Flow

+ References

No definition available.

+ Details

Name:	giii_PercentagePrepaymentOfExcessCashFlowFour
Namespace Prefix:	giii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents percentage prepayment of excess cash flow.

+ References

No definition available.

+ Details

Name:	giii_PercentagePrepaymentOfExcessCashFlowThree
Namespace Prefix:	giii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents percentage prepayment of excess cash flow.

+ References

No definition available.

+ Details

Name:	giii_PercentagePrepaymentOfExcessCashFlowTwo
Namespace Prefix:	giii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

States whether the entity was in compliance with the debt covenants throughout the reporting period, and describes facts and circumstances of any compliance failure.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the debt agreement. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants.

+ References

+ Details

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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

The average effective interest rate during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

+ Details

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

- 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

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

+ Details

Name:	us-gaap_DebtInstrumentPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, 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_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

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

+ References

+ Details

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

- 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_LongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableOtherPayablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=giii_NotesPayableDueOnJune12023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=giii_NotesPayableDueOnDecember12023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

NOTES PAYABLE AND OTHER LIABILITIES - Textuals (Details) $ in Thousands, € in Millions			12 Months Ended
	Apr. 15, 2019 EUR (€)	Dec. 01, 2016 USD ($)	Jan. 31, 2020 USD ($)	Jan. 31, 2019 USD ($)
Debt Instrument [Line Items]
Debt issuance costs			$ 4,600	$ 7,100
Long-term Debt
Debt Instrument [Line Items]
Debt instruments, carrying value			427,860	425,000
Debt discount			22,991	28,382
Senior secured term loan facility (the "Term Loan")
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 350,000
Prepayment of principal amount		$ 50,000
Debt instruments, carrying value		$ 300,000
Floor rate			1.00%
Applicable margin			5.25%
Prepayment percentage of excess cash flow			75.00%
Prepayment percentage of excess cash flow when leverage ratio less than 3.00 to 1.00			50.00%
Leverage ratio description for 50% prepayment			less than 3.00 to 1.00
Prepayment percentage of excess cash flow when leverage ratio less than 2.75 to 1.00			25.00%
Leverage ratio description for 25% prepayment			less than 2.75 to 1.00
Prepayment percentage of excess cash flow when leverage ratio less than 2.25 to 1.00			0.00%
Leverage ratio description for 0% prepayment			less than 2.25 to 1.00
Loan description			Interest on the outstanding principal amount of the Term Loan accrues at a rate equal to the London Interbank Offered Rate (“LIBOR”), subject to a 1% floor, plus an applicable margin of 5.25% or an alternate base rate (defined as the greatest of (i) the “prime rate” as published by the Wall Street Journal from time to time, (ii) the federal funds rate plus 0.5% or (iii) the LIBOR rate for a borrowing with an interest period of one month) plus 4.25%, per annum, payable in cash.
Debt covenant compliance			As of January 31, 2020, the Company was in compliance with these covenants.
Interest rate terms			Interest on the outstanding principal amount of the Term Loan accrues at a rate equal to the London Interbank Offered Rate (“LIBOR”), subject to a 1% floor, plus an applicable margin of 5.25% or an alternate base rate (defined as the greatest of (i) the “prime rate” as published by the Wall Street Journal from time to time, (ii) the federal funds rate plus 0.5% or (iii) the LIBOR rate for a borrowing with an interest period of one month) plus 4.25%, per annum, payable in cash.
Debt issuance costs			$ 18,300
Loan expenses			$ 2,600
Weighted average interest rate			7.58%
Basis points change in interest rate			0.25%
Effect of change on interest expenses			$ 800
Senior secured term loan facility (the "Term Loan") \| LIBOR plus
Debt Instrument [Line Items]
Spread interest rate			4.25%
Senior secured term loan facility (the "Term Loan") \| Federal funds rate plus
Debt Instrument [Line Items]
Spread interest rate			0.50%
Senior secured term loan facility (the "Term Loan") \| Long-term Debt
Debt Instrument [Line Items]
Debt instruments, carrying value			$ 300,000	300,000
Revolving credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 650,000
Debt instrument commitment fee percentage			0.25%
Term of credit agreement			5 years
Loan description			The revolving credit facility contains covenants that, among other things, restrict the Company’s ability, subject to specified exceptions, to incur additional debt; incur liens; sell or dispose of certain assets; merge with other companies; liquidate or dissolve the Company; acquire other companies; make loans, advances, or guarantees; and make certain investments. In certain circumstances, the revolving credit facility also requires the Company to maintain a fixed charge coverage ratio, as defined in the agreement, not less than 1.00 to 1.00 for each period of twelve consecutive fiscal months of the Company.
Debt covenant compliance			As of January 31, 2020, the Company was in compliance with these covenants.
Debt issuance costs			$ 12,400
Weighted average interest rate			3.26%
Maturity date			Dec. 01, 2021
Revolving credit facility \| Federal funds rate plus
Debt Instrument [Line Items]
Spread interest rate			0.50%
LVMH Note
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 125,000
Debt instrument interest rate			2.00%
Maturity date			Jun. 01, 2023
Debt discount			$ 40,000
LVMH Note \| Notes Payable Due On June 1 2023
Debt Instrument [Line Items]
Principal amount of debt			75,000
LVMH Note \| Notes Payable due on December 1, 2023
Debt Instrument [Line Items]
Principal amount of debt			50,000
LVMH Note \| Long-term Debt
Debt Instrument [Line Items]
Debt instruments, carrying value			$ 125,000	$ 125,000
Unsecured Loan
Debt Instrument [Line Items]
Debt instrument interest rate	1.50%
Principal amount of debt \| €	€ 3.0
Maturity date			Apr. 15, 2024
Installment payments \| €	€ 0.2
Unsecured Loan \| Long-term Debt
Debt Instrument [Line Items]
Debt instruments, carrying value			$ 2,860
Trade letters of Credit \| Revolving credit facility
Debt Instrument [Line Items]
Borrowings outstanding			6,500
Standby Letters of Credit \| Revolving credit facility
Debt Instrument [Line Items]
Borrowings outstanding			5,300
Long term liabilities \| Revolving credit facility
Debt Instrument [Line Items]
Borrowings outstanding			$ 0
Minimum \| Revolving credit facility \| LIBOR plus
Debt Instrument [Line Items]
Spread interest rate			1.25%
LIBOR rate for borrowing with an interest period of one month			0.25%
Maximum \| Revolving credit facility \| LIBOR plus
Debt Instrument [Line Items]
Spread interest rate			1.75%
LIBOR rate for borrowing with an interest period of one month			0.75%