Additional basic contribution to savings plan by employees in percentage.

No definition available.

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- Definition

Basic contribution to savings plan by employees in percentage.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan option for employees to remain for maximum additional period.

+ References

No definition available.

+ Details

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- Definition

Employee Contribution Percent

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee retirement age.

+ References

No definition available.

+ Details

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Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of equity in GTI.

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of increase in salaries based on the final average wages.

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of quarterly contributions to each employee's total eligible pay.

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Units of fund that invest in our common stock.

+ References

No definition available.

+ Details

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Namespace Prefix:	gti_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16701-113920

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Balance Type:	na
Period Type:	instant

- Definition

The value of a trust established to hold the stock of an employee compensation and benefits plan as of the balance sheet date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Accumulated Benefit Obligation

-URI http://asc.fasb.org/extlink&oid=6503844

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Balance Type:	credit
Period Type:	instant

- Definition

The amounts in accumulated other comprehensive income related to prior service cost or credit expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (s)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 158

-Paragraph 7

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph s

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Balance Type:	credit
Period Type:	duration

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Target allocation of investments of this type to total plan assets presented on a weighted average basis.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Target allocation maximum percentage of investments of this type to total plan assets presented on a weighted average basis.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its non-pension postretirement benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

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- Definition

Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Value of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan.

+ References

No definition available.

+ Details

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Retirement Plans And Postretirement Benefits (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 years	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Percentage of increase in salaries based on the final average wages	6.00%
Percentage of equity in GTI	50.00%
Option to remain in defined benefit plan for an additional period, in years	5 years
Percentage of quarterly contributions to each employee's total eligible pay	1.00%
Pension and other postretirement benefit contributions	$ 0.9	$ 1.0	$ 0.8
Defined benefit plan, accumulated benefit obligation	213.2	230.1
Employee retirement age, years	65
Prior service credit from stockholders' equity	0.2
Assets of trust approximately	5.3	4.3
Common stock held in employee benefit and compensation trusts, shares	87,206	76,095
Basic contribution to savings plan by employees in percentage	5.00%
Additional basic contribution to savings plan by employees in percentage	45.00%
Stock issued during period, shares, employee savings plan	553,298	433,496	186,237
Stock issued during period, value, employee benefit plan	$ 4.6	$ 4.6	$ 3.3
U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment plan percentage	100.00%
First Of Employee Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Units of fund that invest in our common stock	100.00%
Employee contribution percent	3.00%
Next of Employee Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Units of fund that invest in our common stock	50.00%
Employee contribution percent	2.00%
Equity Securities [Member] \| U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment plan percentage	20.00%
Investment plan maximum	100.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment plan percentage	100.00%
Fixed Income Securities [Member] \| U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment plan percentage	80.00%