XML 63 R51.htm IDEA: XBRL DOCUMENT
v3.21.2

Derivative Instruments - Income Statement (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Commodity Forward Derivative | Designated as Hedging Instrument | Cost of sales |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized | $ (4,498) | $ 1,130 | $ (5,047) | $ 3,939
Interest rate swap contract | Not Designated as Hedging Instrument | Interest expense |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized |  |  | (866) | 0
Interest rate swap contract | Designated as Hedging Instrument | Interest expense |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized | (289) | (1,521) | (1,285) | (1,315)
Foreign currency derivatives | Not Designated as Hedging Instrument | Cost Of Good Sold Other Expense Income [Member] |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized | (264) | $ 217 | (1,893) | 716
Commodity derivative contracts | Not Designated as Hedging Instrument | Cost of sales |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized | $ 242 |  |  | (25)
Commodity derivative contracts | Not Designated as Hedging Instrument | Interest expense |  |  |  |
Derivative Instruments, Gain (Loss) |  |  |  |
Amount of (Gain)/Loss Recognized |  |  | $ 242 | $ 114

X
- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
Name: | us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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 No definition available. + Details
Name: | us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=gti_CommodityForwardDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_CostOfSalesMember
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_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_InterestExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=gti_ForeignCurrencyDerivativesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=gti_CostOfGoodSoldOtherExpenseIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |