Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 99,837	$ 122,882	$ 97,679	$ 38,277
Other current assets	474,785us-gaap_OtherAssetsCurrent	463,700us-gaap_OtherAssetsCurrent
Plant, equipment and timberlands, net	697,608us-gaap_PropertyPlantAndEquipmentNet	723,340us-gaap_PropertyPlantAndEquipmentNet	621,200us-gaap_PropertyPlantAndEquipmentNet
Other assets	289,274glt_OtherAssetsOtherNoncurrent	368,488glt_OtherAssetsOtherNoncurrent
Total assets	1,561,504us-gaap_Assets	1,678,410us-gaap_Assets
Liabilities and Shareholders' Equity
Current liabilities	279,731us-gaap_LiabilitiesCurrent	288,367us-gaap_LiabilitiesCurrent
Long-term debt	398,878us-gaap_LongTermDebtNoncurrent	442,325us-gaap_LongTermDebtNoncurrent
Deferred income taxes	104,016	141,020
Other long-term liabilities	129,770us-gaap_OtherLiabilitiesNoncurrent	122,222us-gaap_OtherLiabilitiesNoncurrent
Total liabilities	912,395us-gaap_Liabilities	993,934us-gaap_Liabilities
Shareholders' equity	649,109us-gaap_StockholdersEquity	684,476us-gaap_StockholdersEquity	539,679us-gaap_StockholdersEquity	490,404us-gaap_StockholdersEquity
Total liabilities and shareholders' equity	1,561,504	1,678,410
Adjustments/ Eliminations [Member]
Assets
Other current assets	(427,777)	(326,045)
Investments in subsidiaries	(1,224,411)	(1,272,221)
Other assets	(17,980)	(15,873)
Total assets	(1,670,168)	(1,614,139)
Liabilities and Shareholders' Equity
Current liabilities	(435,062)	(337,878)
Long-term debt	(572,579)	(320,795)
Deferred income taxes	(12,289)	(8,319)
Other long-term liabilities	5,779	3,409
Total liabilities	(1,014,151)	(663,583)
Shareholders' equity	(656,017)	(950,556)
Total liabilities and shareholders' equity	(1,670,168)	(1,614,139)
Parent Company [Member]
Assets
Cash and cash equivalents	42,208	56,216	43,781	3,063
Other current assets	218,544	208,814
Plant, equipment and timberlands, net	255,255	247,243
Investments in subsidiaries	824,480	803,688
Other assets	121,125	170,060
Total assets	1,461,612	1,486,021
Liabilities and Shareholders' Equity
Current liabilities	403,662	375,535
Long-term debt	250,000	250,000
Deferred income taxes	46,483	70,989
Other long-term liabilities	112,358	105,021
Total liabilities	812,503	801,545
Shareholders' equity	649,109	684,476
Total liabilities and shareholders' equity	1,461,612	1,486,021
Guarantors [Member]
Assets
Cash and cash equivalents	514	501	4,278	2,838
Other current assets	420,451	327,152
Plant, equipment and timberlands, net	991	1,054
Investments in subsidiaries	399,931	468,533
Total assets	821,887	797,240
Liabilities and Shareholders' Equity
Current liabilities	3,394	2,855
Deferred income taxes	(453)	(283)
Total liabilities	2,941	2,572
Shareholders' equity	818,946	794,668
Total liabilities and shareholders' equity	821,887	797,240
Non Guarantors [Member]
Assets
Cash and cash equivalents	57,115	66,165	49,620	32,376
Other current assets	263,567	253,779
Plant, equipment and timberlands, net	441,362	475,043
Other assets	186,129	214,301
Total assets	948,173	1,009,288
Liabilities and Shareholders' Equity
Current liabilities	307,737	247,855
Long-term debt	721,457	513,120
Deferred income taxes	70,275	78,633
Other long-term liabilities	11,633	13,792
Total liabilities	1,111,102	853,400
Shareholders' equity	(162,929)	155,888
Total liabilities and shareholders' equity	$ 948,173	$ 1,009,288

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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