Consolidated Statements Of Shareholders' Equity - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	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, 2017	$ 343,780	$ 34,747	$ 487,230	$ (1,528)	$ (86,178)	$ 459	$ (90,950)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(1,314)		(1,314)
Foreign currency translation adjustment (net of tax of $0)	(11,571)				(11,571)
Derivative financial instruments adjustment (net of tax benefit of $316)	(2,891)					(2,891)
Amortization of prior service costs and net gains or losses (net of tax of $2,312)	7,926						7,926
Cash dividends declared ($0.33 per share)	(10,943)		(10,943)
Stock-based compensation expense	2,780	2,780
Issued upon exercise of stock options & other	1,004	1,004
Tredegar common stock purchased by trust for savings restoration plan			24	(24)
Ending Balance at Sep. 30, 2018	$ 328,771	$ 38,531	$ 474,997	$ (1,552)	$ (97,749)	$ (2,432)	$ (83,024)