Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	GLT
Entity Registrant Name	P. H. Glatfelter Company
Entity Central Index Key	0000041719
Current Fiscal Year End Date	--12-31
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	1-03560
Entity Tax Identification Number	23-0628360
Entity Address, Address Line One	96 South George Street
Entity Address, Address Line Two	Suite 520
Entity Address, City or Town	York
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	17401
City Area Code	717
Entity Incorporation, State or Country Code	PA
Title of 12(b) Security	Common Stock
Document Transition Report	false
Document Quarterly Report	true
Security Exchange Name	NYSE
Local Phone Number	850-0170
Entity Common Stock, Shares Outstanding		44,311,663