Condensed Consolidating Financial Statements - Condensed Consolidating Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents	$ 71,570	$ 99,837	$ 74,785	$ 122,882
Other current assets	478,011us-gaap_OtherAssetsCurrent	474,785us-gaap_OtherAssetsCurrent
Plant, equipment and timberlands, net	662,808us-gaap_PropertyPlantAndEquipmentNet	697,608us-gaap_PropertyPlantAndEquipmentNet
Other assets	274,868glt_OtherAssetsOtherNoncurrent	289,274glt_OtherAssetsOtherNoncurrent
Total assets	1,487,257us-gaap_Assets	1,561,504us-gaap_Assets
Liabilities and Shareholders' Equity
Current liabilities	258,434us-gaap_LiabilitiesCurrent	279,731us-gaap_LiabilitiesCurrent
Long-term debt	379,757us-gaap_LongTermDebtNoncurrent	398,878us-gaap_LongTermDebtNoncurrent
Deferred income taxes	100,455	104,016
Other long-term liabilities	125,742us-gaap_OtherLiabilitiesNoncurrent	129,770us-gaap_OtherLiabilitiesNoncurrent
Total liabilities	864,388us-gaap_Liabilities	912,395us-gaap_Liabilities
Shareholders' equity	622,869us-gaap_StockholdersEquity	649,109us-gaap_StockholdersEquity
Total liabilities and shareholders' equity	1,487,257	1,561,504
Adjustments/ Eliminations [Member]
Assets
Other current assets	(348,100)	(427,777)
Investments in subsidiaries	(1,180,272)	(1,224,411)
Other assets	(87,293)	(17,980)
Total assets	(1,615,665)	(1,670,168)
Liabilities and Shareholders' Equity
Current liabilities	(350,801)	(435,062)
Long-term debt	(506,032)	(572,579)
Deferred income taxes	2,719	(12,289)
Other long-term liabilities	(86,806)	5,779
Total liabilities	(940,920)	(1,014,151)
Shareholders' equity	(674,745)	(656,017)
Total liabilities and shareholders' equity	(1,615,665)	(1,670,168)
Parent Company [Member]
Assets
Cash and cash equivalents	50,133	42,208	41,133	56,216
Other current assets	227,159	218,544
Plant, equipment and timberlands, net	259,875	255,255
Investments in subsidiaries	802,272	824,480
Other assets	126,687	121,125
Total assets	1,466,126	1,461,612
Liabilities and Shareholders' Equity
Current liabilities	434,759	403,662
Long-term debt	250,000	250,000
Deferred income taxes	48,983	46,483
Other long-term liabilities	109,515	112,358
Total liabilities	843,257	812,503
Shareholders' equity	622,869	649,109
Total liabilities and shareholders' equity	1,466,126	1,461,612
Guarantors [Member]
Assets
Cash and cash equivalents	2,583	514	232	501
Other current assets	328,811	420,451
Plant, equipment and timberlands, net	961	991
Investments in subsidiaries	378,000	399,931
Other assets	86,808
Total assets	797,163	821,887
Liabilities and Shareholders' Equity
Current liabilities	4,887	3,394
Deferred income taxes	(453)	(453)
Total liabilities	4,434	2,941
Shareholders' equity	792,729	818,946
Total liabilities and shareholders' equity	797,163	821,887
Non Guarantors [Member]
Assets
Cash and cash equivalents	18,854	57,115	33,420	66,165
Other current assets	270,141	263,567
Plant, equipment and timberlands, net	401,972	441,362
Other assets	148,666	186,129
Total assets	839,633	948,173
Liabilities and Shareholders' Equity
Current liabilities	169,589	307,737
Long-term debt	635,789	721,457
Deferred income taxes	49,206	70,275
Other long-term liabilities	103,033	11,633
Total liabilities	957,617	1,111,102
Shareholders' equity	(117,984)	(162,929)
Total liabilities and shareholders' equity	$ 839,633	$ 948,173

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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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Amount of deferred tax liability attributable to taxable temporary differences, net of deferred tax asset attributable to deductible temporary differences and carryforwards net of valuation allowances expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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