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Pension And Other Post-Retirement Benefits (Tables) | 6 Months Ended
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Jun. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Schedule Of Components Of Net Periodic Benefit Cost For Pension And Other Post-Retirement Benefit Programs | The components of net periodic benefit cost for the pension and other post-retirement benefit programs reflected in the consolidated statements of income are shown below:
| Pension Benefits |  | Other Post-Retirement Benefits
| Three Months Ended June 30, |  | Three Months Ended June 30,
(In thousands) | 2018 |  | 2017 |  | 2018 |  | 2017
Service cost | $ | 5 |  |  | $ | 58 |  |  | $ | 10 |  |  | $ | 9 |
Interest cost | 2,882 |  |  | 3,164 |  |  | 69 |  |  | 77 |
Expected return on plan assets | (3,761 | ) |  | (3,737 | ) |  | — |  |  | — |
Amortization of prior service costs, gains or losses and net transition asset | 3,428 |  |  | 3,122 |  |  | (54 | ) |  | (62 | )
Net periodic benefit cost | $ | 2,554 |  |  | $ | 2,607 |  |  | $ | 25 |  |  | $ | 24 |
| Pension Benefits |  | Other Post-Retirement Benefits
| Six Months Ended June 30, |  | Six Months Ended June 30,
| 2018 |  | 2017 |  | 2018 |  | 2017
Service cost | $ | 10 |  |  | $ | 116 |  |  | $ | 20 |  |  | $ | 18 |
Interest cost | 5,764 |  |  | 6,328 |  |  | 138 |  |  | 153 |
Expected return on plan assets | (7,522 | ) |  | (7,473 | ) |  | — |  |  | — |
Amortization of prior service costs, (gains) losses and net transition asset | 6,856 |  |  | 6,245 |  |  | (108 | ) |  | (123 | )
Net periodic benefit cost | $ | 5,108 |  |  | $ | 5,216 |  |  | $ | 50 |  |  | $ | 48 |

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- Definition Schedule Of Components Of Net Periodic Benefit Cost For Pension And Other Post-Retirement Benefit Programs [Table Text Block] + References No definition available. + Details
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Namespace Prefix: | tg_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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