Consolidated Statements Of Shareholders' Equity - USD ($)	Total	Common Stock	Retained Earnings	Trust for Savings Restoration Plan	Foreign Currency Translation	Gain (Loss) on Derivative Financial Instruments	Pension & Other Post-retirement Benefit Adjustment
Beginning Balance at Dec. 31, 2018	$ 354,857,000	$ 38,892,000	$ 497,511,000	$ (1,559,000)	$ (96,940,000)	$ (1,601,000)	$ (81,446,000)
Net income (loss)	34,261,000		34,261,000
Foreign currency translation adjustment (net of tax benefit of $1,106)	(283,000)				(283,000)
Derivative financial instruments adjustment (net of tax benefit of $887)	268,000					268,000
Amortization of prior service costs and net gains or losses (net of tax of $1,671)	4,158,000						4,158,000
Dividends, Common Stock, Cash	(7,320,000)		(7,320,000)
Stock-based compensation expense	3,189,000	3,189,000
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(854,000)	(854,000)
Tredegar common stock purchased by trust for savings restoration plan			16,000	(16,000)
Ending Balance at Jun. 30, 2019	388,276,000	41,227,000	524,468,000	(1,575,000)	(97,223,000)	(1,333,000)	(77,288,000)
Foreign currency translation adjustment, tax (benefit)	0
Derivative financial instruments adjustment, tax (benefit)	$ (51,000)
Cash dividends declared, per share	$ 0.22
Amortization of prior service costs and net gains or losses, tax	$ 1,185,000
Beginning Balance at Mar. 31, 2019	372,621,000	39,587,000	513,653,000	(1,568,000)	(97,730,000)	(1,954,000)	(79,367,000)
Net income (loss)	14,477,000		14,477,000
Foreign currency translation adjustment (net of tax benefit of $1,106)	507,000				507,000
Derivative financial instruments adjustment (net of tax benefit of $887)	621,000					621,000
Amortization of prior service costs and net gains or losses (net of tax of $1,671)	2,079,000						2,079,000
Dividends, Common Stock, Cash	(3,669,000)		(3,669,000)
Stock-based compensation expense	1,679,000	1,679,000
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(39,000)	(39,000)
Tredegar common stock purchased by trust for savings restoration plan			7,000	(7,000)
Ending Balance at Jun. 30, 2019	388,276,000	41,227,000	524,468,000	(1,575,000)	(97,223,000)	(1,333,000)	(77,288,000)
Foreign currency translation adjustment, tax (benefit)	0
Derivative financial instruments adjustment, tax (benefit)	$ (134,000)
Cash dividends declared, per share	$ 0.11
Amortization of prior service costs and net gains or losses, tax	$ 593,000
Beginning Balance at Dec. 31, 2019	376,749,000	45,514,000	530,478,000	(1,592,000)	(100,663,000)	(1,307,000)	(95,681,000)
Net income (loss)	(11,126,000)
Foreign currency translation adjustment (net of tax benefit of $1,106)	(12,003,000)				(12,003,000)
Derivative financial instruments adjustment (net of tax benefit of $887)	(2,517,000)					(2,517,000)
Amortization of prior service costs and net gains or losses (net of tax of $1,671)	5,862,000						5,862,000
Dividends, Common Stock, Cash	8,025,000		8,025,000
Stock-based compensation expense	2,520,000	2,520,000
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation		(586,000)
Tredegar common stock purchased by trust for savings restoration plan			(18,000)	18,000
Ending Balance at Jun. 30, 2020	350,874,000	47,448,000	511,345,000	(1,610,000)	(112,666,000)	(3,824,000)	(89,819,000)
Foreign currency translation adjustment, tax (benefit)	1,106,000
Derivative financial instruments adjustment, tax (benefit)	$ 887,000
Cash dividends declared, per share	$ 0.24
Amortization of prior service costs and net gains or losses, tax	$ 1,671,000
Beginning Balance at Mar. 31, 2020	338,590,000	46,054,000	504,161,000	(1,601,000)	(112,192,000)	(5,082,000)	(92,750,000)
Net income (loss)	11,196,000
Foreign currency translation adjustment (net of tax benefit of $1,106)	(474,000)				(474,000)
Derivative financial instruments adjustment (net of tax benefit of $887)	1,258,000					1,258,000
Amortization of prior service costs and net gains or losses (net of tax of $1,671)	2,931,000						2,931,000
Dividends, Common Stock, Cash	4,021,000		4,021,000
Stock-based compensation expense	1,394,000	1,394,000
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(586,000)
Tredegar common stock purchased by trust for savings restoration plan			(9,000)	9,000
Ending Balance at Jun. 30, 2020	350,874,000	$ 47,448,000	$ 511,345,000	$ (1,610,000)	$ (112,666,000)	$ (3,824,000)	$ (89,819,000)
Foreign currency translation adjustment, tax (benefit)	177,000
Derivative financial instruments adjustment, tax (benefit)	$ 339,000
Cash dividends declared, per share	$ 0.12
Amortization of prior service costs and net gains or losses, tax	$ 835,000