| Cover | Aug. 06, 2020 | Aug. 05, 2020 | May 06, 2020 |
| Cover [Abstract] | |||
| Entity Incorporation, State or Country Code | DE | ||
| Document Type | 8-K | ||
| Document Period End Date | Aug. 5, 2020 | ||
| Entity Registrant Name | GRAFTECH INTERNATIONAL LTD. | ||
| Entity File Number | 1-13888 | ||
| Entity Tax Identification Number | 27-2496053 | ||
| Entity Address, Address Line One | 982 Keynote Circle | ||
| Entity Address, City or Town | Brooklyn Heights | ||
| Entity Address, State or Province | OH | ||
| Entity Address, Postal Zip Code | 44131 | ||
| City Area Code | 216 | ||
| Local Phone Number | 676-2000 | ||
| Written Communications | false | ||
| Soliciting Material | false | ||
| Pre-commencement Tender Offer | false | ||
| Pre-commencement Issuer Tender Offer | false | ||
| Title of each class | Common stock, $0.01 par value per share | ||
| Trading Symbol(s) | EAF | ||
| Name of each exchange on which registered | NYSE | ||
| Entity Emerging Growth Company | false | ||
| Entity Central Index Key | 0000931148 | ||
| Amendment Flag | false |
