Borrowing Threshold

No definition available.

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

- Definition

Borrowing Threshold Percentage

+ References

No definition available.

+ Details

Name:	gti_BorrowingThresholdPercentage
Namespace Prefix:	gti_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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

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:	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

Amount of increase (decrease) of the credit facility.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

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

- 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

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
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

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

- Details

Name:	us-gaap_DebtInstrumentAxis=gti_A2018TermLoanFacilityMember
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_A2018RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
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Period Type:

Debt And Liquidity (2018 Revolving Credit Facility) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	May 30, 2022	Feb. 28, 2018
2018 Term Loan Facility
Debt Instrument [Line Items]
Borrowing Threshold	$ 35,000,000
Borrowing Threshold Percentage	35.00%
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,250,000,000			$ 1,500,000,000
2018 Term Loan Facility \| Adjusted LIBO Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.00%
Debt Instrument, Basis Spread on Variable Rate, Decrease Upon Achievement Of Specific Credit Ratings	0.25%
2018 Term Loan Facility \| ABR
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
2018 Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Line of Credit	$ 0	$ 0
Letters of Credit Outstanding, Amount	$ 3,000,000	$ 3,000,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.25%
2018 Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net	$ 80,000,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 330,000,000		$ 250,000,000
2018 Revolving Credit Facility \| Adjusted LIBO Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Debt Instrument, Basis Spread on Variable Rate, Decrease Upon Achievement Of Specific Credit Ratings	0.25%