Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For interim financial reporting, the Company estimates the annual tax rate based on projected taxable income for the full year and records a quarterly income tax provision in accordance with ASC No. 740-270 "Accounting for Income Taxes in Interim Periods." These interim estimates are subject to variation due to several factors, including our ability to accurately forecast our pre-tax and taxable income and loss by jurisdiction, changes in laws or regulations, and expenses or losses for which tax benefits are not recognized. Jurisdictions with a projected loss for the year or an actual year-to-date loss where no tax benefit can be recognized are excluded from the estimated annual effective tax rate. The impact of including these jurisdictions on the quarterly effective tax rate calculations could result in a higher or lower effective tax rate during a particular quarter, based upon the mix and timing of actual earnings verses annual projections. On December 22, 2017, the 2017 Tax Cuts and Jobs Act (the "Tax Act") was enacted into law and the new legislation contains several key tax provisions that require recognition of the effect of the tax law changes in the period of enactment. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118"), which allows us to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. The Company is applying the guidance in SAB 118 when accounting for the enactment date effects of the Tax Act. The Company determined that the remeasurement of if its deferred tax assets and liabilities, transition tax liability, related Tax Act impacts on state taxes, and tax liability associated with investments in non-US subsidiaries where book basis exceeds tax basis are provisional amounts and reasonable estimates as of December 31, 2017. At March 31, 2018, the Company has not completed its accounting for all the tax effects of the Tax Act and has not made any additional measurement period adjustments. Measurement period adjustments will be made as the Company finalizes its 2017 tax returns during 2018, completes its foreign earnings and profit computations, completes its foreign tax computations, and finalizes calculations of its deferred tax asset and liabilities in historical foreign earnings and operations. Any adjustments to the Company’s provisional estimates will be recorded in the period when the Company’s analysis is complete. The impact of the Tax Act may differ from our provisional estimates, possibly materially, during the one-year measurement period due to further refinement of the Company’s calculations. Further, additional guidance may be issued to address questions that arise because of the Tax Act, which may affect actions the Company may take as a result of the Tax Act. The Tax Act subjects a U.S. shareholder to tax on GILTI earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for GILTI, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. Due to the complexity of the new GILTI tax rules, the Company is continuing to evaluate this provision of the Tax Act and the accounting policy choice of either (1) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current-period expense when incurred or (2) factoring such amounts into the Company’s measurement of its deferred taxes. Since the future impacts on taxable income depends on a number of different aspects of estimated future results of global operations, the policy decision has not yet been made. All unrecognized tax positions could impact the Company's effective tax rate if recognized. With respect to penalties and interest incurred from income tax assessments or related to unrecognized tax benefits, the Company’s policy is to classify penalties as provision for income taxes and interest as interest expense in its consolidated statement of income. There were no material income tax penalties or interest accrued during the three months ended March 31, 2018 or 2017. SWM's effective tax rate from continuing operations was 25.6% and 34.3% for the three months ended March 31, 2018 and 2017, respectively. The decrease was materially due to the favorable US tax rate reduction offset by other unfavorable US tax reform adjustments.

Income Taxes

For interim financial reporting, the Company estimates the annual tax rate based on projected taxable income for the full year and records a quarterly income tax provision in accordance with ASC No. 740-270 "Accounting for Income Taxes in Interim Periods." These interim estimates are subject to variation due to several factors, including our ability to accurately forecast our pre-tax and taxable income and loss by jurisdiction, changes in laws or regulations, and expenses or losses for which tax benefits are not recognized. Jurisdictions with a projected loss for the year or an actual year-to-date loss where no tax benefit can be recognized are excluded from the estimated annual effective tax rate. The impact of including these jurisdictions on the quarterly effective tax rate calculations could result in a higher or lower effective tax rate during a particular quarter, based upon the mix and timing of actual earnings verses annual projections.

On December 22, 2017, the 2017 Tax Cuts and Jobs Act (the "Tax Act") was enacted into law and the new legislation contains several key tax provisions that require recognition of the effect of the tax law changes in the period of enactment. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act ("SAB 118"), which allows us to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. The Company is applying the guidance in SAB 118 when accounting for the enactment date effects of the Tax Act. The Company determined that the remeasurement of if its deferred tax assets and liabilities, transition tax liability, related Tax Act impacts on state taxes, and tax liability associated with investments in non-US subsidiaries where book basis exceeds tax basis are provisional amounts and reasonable estimates as of December 31, 2017. At March 31, 2018, the Company has not completed its accounting for all the tax effects of the Tax Act and has not made any additional measurement period adjustments. Measurement period adjustments will be made as the Company finalizes its 2017 tax returns during 2018, completes its foreign earnings and profit computations, completes its foreign tax computations, and finalizes calculations of its deferred tax asset and liabilities in historical foreign earnings and operations. Any adjustments to the Company’s provisional estimates will be recorded in the period when the Company’s analysis is complete.

The impact of the Tax Act may differ from our provisional estimates, possibly materially, during the one-year measurement period due to further refinement of the Company’s calculations. Further, additional guidance may be issued to address questions that arise because of the Tax Act, which may affect actions the Company may take as a result of the Tax Act.

The Tax Act subjects a U.S. shareholder to tax on GILTI earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for GILTI, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. Due to the complexity of the new GILTI tax rules, the Company is continuing to evaluate this provision of the Tax Act and the accounting policy choice of either (1) treating taxes due on future U.S. inclusions in taxable income related to GILTI as a current-period expense when incurred or (2) factoring such amounts into the Company’s measurement of its deferred taxes. Since the future impacts on taxable income depends on a number of different aspects of estimated future results of global operations, the policy decision has not yet been made.

All unrecognized tax positions could impact the Company's effective tax rate if recognized. With respect to penalties and interest incurred from income tax assessments or related to unrecognized tax benefits, the Company’s policy is to classify penalties as provision for income taxes and interest as interest expense in its consolidated statement of income. There were no material income tax penalties or interest accrued during the three months ended March 31, 2018 or 2017.

SWM's effective tax rate from continuing operations was 25.6% and 34.3% for the three months ended March 31, 2018 and 2017, respectively. The decrease was materially due to the favorable US tax rate reduction offset by other unfavorable US tax reform adjustments.