Investments	6 Months Ended
Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments	In August 2007 and December 2008, the Company made an aggregate investment of $7.5 million in kaléo, a privately held specialty pharmaceutical company dedicated to building innovative solutions for serious and life-threatening medical conditions. The mission of kaléo is to provide products that empower patients to confidently take control of their medical conditions. Tredegar owns Series A-3 Preferred Stock and Series B Preferred Stock in kaléo that, taken together, represents on a fully-diluted basis an approximate 20% interest in kaléo. Tredegar accounts for its investment in kaléo under the fair value method. At the time of the initial investment, the Company elected the fair value option of accounting since its investment objectives were similar to those of venture capitalists, which typically do not have controlling financial interests. At June 30, 2018, the estimated fair value of the Company’s investment was $68.0 million, up from $62.2 million and $54.0 million as of March 31, 2018 and December 31, 2017, respectively. The change in the estimated fair value of the Company’s holding in kaléo since the end of 2017 primarily relates to the difference from discounting between the present value of projected cash flows at June 30, 2018 versus December 31, 2017 (i.e., the time value of money), changes in cash flow projections for various scenarios and the assessment of the risk-adjusted discount rate appropriate for the various scenarios. Kaléo’s stock is not publicly traded. The valuation estimate in this situation is based on projection assumptions or Level 3 inputs that have a wide range of possible outcomes. There are numerous assumptions and Level 3 inputs that, if changed, impact the projection of kaléo’s future cash flows, and the probability of actually achieving those cash flows. For example, there are various regulatory and legal enforcement efforts related to the markets for kaléo’s products, which could affect kaléo’s efforts to market those products. Moreover, many of the assumptions and inputs are interrelated, including key assumptions for kaléo’s projected market share, pricing and net margins after chargebacks, discounts, rebates, copays and returns. Accordingly, determining the sensitivity of changes in estimated fair value to the change in one assumption is not practical. Ultimately, the true value of the Company’s ownership interest in kaléo will be determined if and when a liquidity event occurs, and the ultimate value could be materially different from the $68.0 million estimated fair value reflected in the Company’s financial statements at June 30, 2018. Unrealized gains (losses) associated with this investment are included in “Other income (expense), net” in the consolidated statements of income and separately stated in the segment operating profit table in Note 11. Subsequent to its most recent investment (December 15, 2008), and until the next round of financing, the Company believes fair value estimates are based upon Level 3 inputs since there is no secondary market for its ownership interest. Accordingly, until the next round of financing or any other significant financial transaction, value estimates will primarily be based on assumptions related to meeting cash flow projections and discounting of these factors for their high degree of risk. If kaléo does not meet its projected cash flows or related risks are unfavorable versus the most recent valuation, or a new round of financing or other significant financial transaction indicates a lower enterprise value, then the Company’s estimate of the fair value of its ownership interest in kaléo is likely to decline. Adjustments to the estimated fair value of this investment will be made in the period upon which such changes can be quantified. The Company’s investment in the Harbinger Fund had a carrying value (included in “Other assets and deferred charges”) of $1.6 million and $1.7 million at June 30, 2018 and December 31, 2017, respectively. The carrying value at June 30, 2018 reflected Tredegar’s cost basis in its investment in the Harbinger Fund, net of total withdrawal proceeds received and unrealized losses. Based on an observable price change, the Company recorded an unrealized loss of $0.1 million in the second quarter and first six months of 2018 (none in 2017). No withdrawal proceeds were received in the first six months of 2017 or 2018. The timing and amount of future installments of withdrawal proceeds, which commenced in August 2010, were not known as of June 30, 2018. The Company has determined that there is no readily determinable fair value for the Harbinger Fund and has elected to record its investment in the Harbinger Fund at cost, less impairment, adjusted for observable price changes. Gains on the Company’s investment in the Harbinger Fund will be recognized when there are positive observable price changes, including when the amounts expected to be collected from any withdrawal from the investment are known, which will likely be when cash in excess of the remaining carrying value is received. Losses will be recognized when management believes through observable methods that it is probable that future withdrawal proceeds will not exceed the remaining carrying value.

In August 2007 and December 2008, the Company made an aggregate investment of $7.5 million in kaléo, a privately held specialty pharmaceutical company dedicated to building innovative solutions for serious and life-threatening medical conditions. The mission of kaléo is to provide products that empower patients to confidently take control of their medical conditions. Tredegar owns Series A-3 Preferred Stock and Series B Preferred Stock in kaléo that, taken together, represents on a fully-diluted basis an approximate 20% interest in kaléo. Tredegar accounts for its investment in kaléo under the fair value method. At the time of the initial investment, the Company elected the fair value option of accounting since its investment objectives were similar to those of venture capitalists, which typically do not have controlling financial interests.

At June 30, 2018, the estimated fair value of the Company’s investment was $68.0 million, up from $62.2 million and $54.0 million as of March 31, 2018 and December 31, 2017, respectively.

The change in the estimated fair value of the Company’s holding in kaléo since the end of 2017 primarily relates to the difference from discounting between the present value of projected cash flows at June 30, 2018 versus December 31, 2017 (i.e., the time value of money), changes in cash flow projections for various scenarios and the assessment of the risk-adjusted discount rate appropriate for the various scenarios. Kaléo’s stock is not publicly traded. The valuation estimate in this situation is based on projection assumptions or Level 3 inputs that have a wide range of possible outcomes.

There are numerous assumptions and Level 3 inputs that, if changed, impact the projection of kaléo’s future cash flows, and the probability of actually achieving those cash flows. For example, there are various regulatory and legal enforcement efforts related to the markets for kaléo’s products, which could affect kaléo’s efforts to market those products. Moreover, many of the assumptions and inputs are interrelated, including key assumptions for kaléo’s projected market share, pricing and net margins after chargebacks, discounts, rebates, copays and returns. Accordingly, determining the sensitivity of changes in estimated fair value to the change in one assumption is not practical.

Ultimately, the true value of the Company’s ownership interest in kaléo will be determined if and when a liquidity event occurs, and the ultimate value could be materially different from the $68.0 million estimated fair value reflected in the Company’s financial statements at June 30, 2018.

Unrealized gains (losses) associated with this investment are included in “Other income (expense), net” in the consolidated statements of income and separately stated in the segment operating profit table in Note 11. Subsequent to its most recent investment (December 15, 2008), and until the next round of financing, the Company believes fair value estimates are based upon Level 3 inputs since there is no secondary market for its ownership interest. Accordingly, until the next round of financing or any other significant financial transaction, value estimates will primarily be based on assumptions related to meeting cash flow projections and discounting of these factors for their high degree of risk. If kaléo does not meet its projected cash flows or related risks are unfavorable versus the most recent valuation, or a new round of financing or other significant financial transaction indicates a lower enterprise value, then the Company’s estimate of the fair value of its ownership interest in kaléo is likely to decline. Adjustments to the estimated fair value of this investment will be made in the period upon which such changes can be quantified.

The Company’s investment in the Harbinger Fund had a carrying value (included in “Other assets and deferred charges”) of $1.6 million and $1.7 million at June 30, 2018 and December 31, 2017, respectively. The carrying value at June 30, 2018 reflected Tredegar’s cost basis in its investment in the Harbinger Fund, net of total withdrawal proceeds received and unrealized losses. Based on an observable price change, the Company recorded an unrealized loss of $0.1 million in the second quarter and first six months of 2018 (none in 2017). No withdrawal proceeds were received in the first six months of 2017 or 2018. The timing and amount of future installments of withdrawal proceeds, which commenced in August 2010, were not known as of June 30, 2018.

The Company has determined that there is no readily determinable fair value for the Harbinger Fund and has elected to record its investment in the Harbinger Fund at cost, less impairment, adjusted for observable price changes. Gains on the Company’s investment in the Harbinger Fund will be recognized when there are positive observable price changes, including when the amounts expected to be collected from any withdrawal from the investment are known, which will likely be when cash in excess of the remaining carrying value is received. Losses will be recognized when management believes through observable methods that it is probable that future withdrawal proceeds will not exceed the remaining carrying value.