Debt Instrument, Annual Amortization Rate, Amount

No definition available.

Name:	gti_DebtInstrumentAnnualAmortizationRateAmount
Namespace Prefix:	gti_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Basis Spread on Variable Rate, Decrease Upon Achievement Of Specific Credit Ratings

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Basis Spread on Variable Rate, Increase (Decrease)

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Variable Rate

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Equity Interest Pledge

+ References

No definition available.

+ Details

Name:	gti_EquityInterestPledge
Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Increase in Borrowing Capacity.

+ References

No definition available.

+ Details

Name:	gti_IncreaseInBorrowingCapacity
Namespace Prefix:	gti_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Repayment Of Excess Cashflow Percentage

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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 https://asc.fasb.org/extlink&oid=120391452&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 https://asc.fasb.org/extlink&oid=126897435&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 https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

+ Details

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

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

Name:	us-gaap_RatioOfIndebtednessToNetCapital1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=gti_A2018CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	gti_ContingentEventAxis=gti_ContingentEventOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gti_ContingentEventAxis=gti_ContingentEventTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
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Balance Type:
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- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember
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Debt And Liquidity (2018 Term Loan and 2018 Revolving Credit Facility) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Feb. 28, 2021	Dec. 31, 2022	May 31, 2022	Dec. 31, 2021	Jun. 30, 2018	Feb. 28, 2018
2018 Credit Agreement [Member]
Debt Instrument [Line Items]
Equity Interest Pledge		65.00%
Ratio of Indebtedness to Net Capital						4.00
Line of Credit [Member] \| 2018 Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Instrument, Annual Amortization Rate, Amount		$ 112,500,000
Repayment Of Excess Cashflow Percentage						75.00%
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Contingent Event One [Member]
Debt Instrument [Line Items]
Repayment Of Excess Cashflow Percentage						50.00%
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Contingent Event Two [Member]
Debt Instrument [Line Items]
Repayment Of Excess Cashflow Percentage						0.00%
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate, Decrease Upon Achievement Of Specific Credit Ratings		0.50%			1.00%
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Minimum [Member] \| Contingent Event One [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						1.25
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Maximum \| Contingent Event One [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital						1.75
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| Adjusted LIBO Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		3.00%
Basis spread on variable rate, decrease	0.50%
Debt Instrument, Basis Spread on Variable Rate, Decrease Upon Achievement Of Specific Credit Ratings	0.25%
Line of Credit [Member] \| 2018 Credit Agreement [Member] \| ABR [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Line of Credit [Member] \| Term Loan Facility
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,250,000,000				$ 1,500,000,000
Revolving Credit Facility [Member] \| 2018 Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		330,000,000	$ 250,000,000
Increase in Borrowing Capacity			$ 80,000,000
Amount Outstanding		0		$ 0
Letters of Credit Outstanding, Amount		$ 3,000,000		$ 3,300,000
Revolving Credit Facility [Member] \| 2018 Credit Agreement [Member] \| ABR [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.00%
Revolving Credit Facility [Member] \| 2018 Credit Agreement [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		3.00%