Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	TREDEGAR CORP
Entity Central Index Key	0000850429
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		33,176,024
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Well-known Seasoned Issuer	No
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 608,660,223