Shareholder Rights Agreement (Narrative) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Warrants and Rights Note Disclosure [Abstract]
Shareholder Rights Redemption Payment	$ 0

Amount paid to shareholders to redeem shareholder rights per Shareholder Rights Agreement.

No definition available.

Name:	tg_ShareholderRightsRedemptionPayment
Namespace Prefix:	tg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration