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Financial Derivatives and Hedging Activities (Details 1) (Not designated as hedging [Member], Forward foreign currency exchange contracts [Member]) In Thousands, unless otherwise specified	Mar. 31, 2013 Euro / U.S. dollar [Member] EUR (€)	Dec. 31, 2012 Euro / U.S. dollar [Member] EUR (€)	Mar. 31, 2013 Euro / British Pound [Member] EUR (€)	Dec. 31, 2012 Euro / British Pound [Member] EUR (€)	Mar. 31, 2013 U.S. dollar / Canadian dollar [Member] CAD	Dec. 31, 2012 U.S. dollar / Canadian dollar [Member] CAD	Mar. 31, 2013 U.S Dollar / Euro [Member] USD ($)	Dec. 31, 2012 U.S Dollar / Euro [Member] USD ($)	Mar. 31, 2013 U.S. dollar / British Pound [Member] USD ($)	Dec. 31, 2012 U.S. dollar / British Pound [Member] USD ($)
Sell / Buy
Sell Notional	€ 13,000	€ 13,000	€ 4,000	€ 4,000	2,000	2,000		$ 2,000	$ 2,000

X

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Namespace Prefix:	glt_
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X

- Definition

Aggregate notional amount of foreign currency exchange rate derivatives. Notional amount refers to the number of currency units specified in the foreign currency derivative contract.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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