Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The effective tax rates for the three months ended September 30, 2018 and 2017 were 18.5% and 22.9%, respectively. The decrease in the effective tax rate for the three months ended September 30, 2018 relative to the prior comparable period was principally due to the decrease in the U.S. statutory tax rate from 35% to 21% and other U.S. tax law changes. The effective tax rates for the nine months ended September 30, 2018 and 2017 were 19.6% and 25.3%, respectively. The decrease in the effective tax rate for the nine months ended September 30, 2018 relative to the prior comparable period was primarily driven by the decrease in the U.S. statutory tax rate from 35% to 21% and other U.S. tax law changes. The discrete items for the three and nine months ended September 30, 2018 primarily resulted from the net tax benefit from stock award exercises. The discrete items for the three and nine months ended September 30, 2017 principally resulted from adjustments to the provision based on filed tax returns in foreign jurisdictions and the effect of the settlement of the 2013 IRS audit. Additionally, the discrete items for the nine months ended September 30, 2017 also included the tax effect of the gain on the sale of PMI. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the U.S. bill commonly referred to as the Tax Cuts and Jobs Act (“Tax Reform Act”). In accordance with the SAB 118 guidance, the Company recognized the provisional tax impacts related to deemed repatriated earnings and the benefit for the revaluation of deferred tax assets and liabilities in its consolidated financial statements for the year ended December 31, 2017. For the nine months ended September 30, 2018, the Company recorded a $1.3 million tax benefit, which resulted in a 0.2% decrease in the effective tax rate, as an adjustment to the provisional estimates as a result of additional regulatory guidance and changes in interpretations and assumptions the Company has made as a result of the Tax Reform Act. In accordance with SAB 118, any additional adjustment to the financial reporting impact of the Tax Reform Act will be completed by the fourth quarter of 2018. Dover and its subsidiaries file tax returns in the U.S., including various state and local returns and in other foreign jurisdictions. We believe adequate provision has been made for all income tax uncertainties. The Company is routinely audited by taxing authorities in its filing jurisdictions, and a number of these audits are currently underway. The Company believes that within the next twelve months uncertain tax positions may be resolved and statutes of limitations will expire, which could result in a decrease in the gross amount of unrecognized tax benefits of approximately zero to $10.6 million.

12. Income Taxes

The effective tax rates for the three months ended September 30, 2018 and 2017 were 18.5% and 22.9%, respectively. The decrease in the effective tax rate for the three months ended September 30, 2018 relative to the prior comparable period was principally due to the decrease in the U.S. statutory tax rate from 35% to 21% and other U.S. tax law changes.

The effective tax rates for the nine months ended September 30, 2018 and 2017 were 19.6% and 25.3%, respectively. The decrease in the effective tax rate for the nine months ended September 30, 2018 relative to the prior comparable period was primarily driven by the decrease in the U.S. statutory tax rate from 35% to 21% and other U.S. tax law changes.

The discrete items for the three and nine months ended September 30, 2018 primarily resulted from the net tax benefit from stock award exercises. The discrete items for the three and nine months ended September 30, 2017 principally resulted from adjustments to the provision based on filed tax returns in foreign jurisdictions and the effect of the settlement of the 2013 IRS audit. Additionally, the discrete items for the nine months ended September 30, 2017 also included the tax effect of the gain on the sale of PMI.

On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the U.S. bill commonly referred to as the Tax Cuts and Jobs Act (“Tax Reform Act”). In accordance with the SAB 118 guidance, the Company recognized the provisional tax impacts related to deemed repatriated earnings and the benefit for the revaluation of deferred tax assets and liabilities in its consolidated financial statements for the year ended December 31, 2017. For the nine months ended September 30, 2018, the Company recorded a $1.3 million tax benefit, which resulted in a 0.2% decrease in the effective tax rate, as an adjustment to the provisional estimates as a result of additional regulatory guidance and changes in interpretations and assumptions the Company has made as a result of the Tax Reform Act. In accordance with SAB 118, any additional adjustment to the financial reporting impact of the Tax Reform Act will be completed by the fourth quarter of 2018.

Dover and its subsidiaries file tax returns in the U.S., including various state and local returns and in other foreign jurisdictions. We believe adequate provision has been made for all income tax uncertainties. The Company is routinely audited by taxing authorities in its filing jurisdictions, and a number of these audits are currently underway. The Company believes that within the next twelve months uncertain tax positions may be resolved and statutes of limitations will expire, which could result in a decrease in the gross amount of unrecognized tax benefits of approximately zero to $10.6 million.