Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income taxes The provision for income taxes for the first nine months of 2018 reflected an estimated annual tax rate of 24 percent, compared to 32 percent for the first nine months of 2017, excluding the discrete items discussed in the following paragraph. The decrease was primarily due to the reduction in the U.S. corporate tax rate beginning January 1, 2018, along with other changes in the geographic mix of profits from a tax perspective. The 2018 provision for income taxes for the first nine months of 2018 also included a $154 million reduction to the provisionally estimated charge of $2.371 billion recognized during the fourth quarter of 2017 due to enactment of U.S. tax reform legislation. The $154 million benefit revises the estimated impact of the write-down of U.S. net deferred tax assets to reflect the reduction in the U.S. corporate tax rate from 35 percent to 21 percent. This benefit primarily related to the decision to make an additional discretionary pension contribution of $1.0 billion to U.S. pension plans in the third quarter of 2018 treated as deductible on the 2017 U.S. tax return. The provision for income taxes for the first nine months of 2018 also includes a charge of $59 million to correct for an error which resulted in an understatement of the valuation allowance offsetting deferred tax assets for prior years. This error had the effect of overstating profit by $17 million, $33 million and $9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Management has concluded that the error was not material to any period presented. In addition, a discrete tax benefit of $52 million was recorded in the first nine months of 2018, compared to $45 million in the first nine months of 2017, for the settlement of stock-based compensation awards with associated tax deductions in excess of cumulative U.S. GAAP compensation expense. The provision for income taxes for the first nine months of 2018 also included a $25 million benefit for the release of a valuation allowance against the deferred tax assets of a non-U.S. subsidiary. The provision for income taxes for the first nine months of 2017 also included a $15 million increase to prior year taxes related to non-U.S. restructuring costs. Our analysis of U.S. tax reform legislation, updated through September 30, 2018, resulted in no other changes to the 2017 year-end provisional charge. We will continue to update our calculations as additional required information is prepared and analyzed, interpretations and assumptions are refined, and additional guidance is issued. These updates could significantly impact the provision for income taxes, the amount of taxes payable and the deferred tax asset and liability balances. We account for the new U.S. tax on global intangible low-taxed income as a period cost. On January 31, 2018, we received a Revenue Agent's Report from the Internal Revenue Service (IRS) indicating the end of the field examination of our U.S. income tax returns for 2010 to 2012. In the audits of 2007 to 2012 including the impact of a loss carryback to 2005, the IRS has proposed to tax in the United States profits earned from certain parts transactions by Caterpillar SARL, based on the IRS examination team's application of the "substance-over-form" or "assignment-of-income" judicial doctrines. We are vigorously contesting the proposed increases to tax and penalties for these years of approximately $2.3 billion. We believe that the relevant transactions complied with applicable tax laws and did not violate judicial doctrines. We have filed U.S. income tax returns on this same basis for years after 2012. Based on the information currently available, we do not anticipate a significant increase or decrease to our unrecognized tax benefits for this matter within the next 12 months. We currently believe the ultimate disposition of this matter will not have a material adverse effect on our consolidated financial position, liquidity or results of operations.

Income taxes

The provision for income taxes for the first nine months of 2018 reflected an estimated annual tax rate of 24 percent, compared to 32 percent for the first nine months of 2017, excluding the discrete items discussed in the following paragraph. The decrease was primarily due to the reduction in the U.S. corporate tax rate beginning January 1, 2018, along with other changes in the geographic mix of profits from a tax perspective.

The 2018 provision for income taxes for the first nine months of 2018 also included a $154 million reduction to the provisionally estimated charge of $2.371 billion recognized during the fourth quarter of 2017 due to enactment of U.S. tax reform legislation. The $154 million benefit revises the estimated impact of the write-down of U.S. net deferred tax assets to reflect the reduction in the U.S. corporate tax rate from 35 percent to 21 percent. This benefit primarily related to the decision to make an additional discretionary pension contribution of $1.0 billion to U.S. pension plans in the third quarter of 2018 treated as deductible on the 2017 U.S. tax return. The provision for income taxes for the first nine months of 2018 also includes a charge of $59 million to correct for an error which resulted in an understatement of the valuation allowance offsetting deferred tax assets for prior years. This error had the effect of overstating profit by $17 million, $33 million and $9 million for the years ended December 31, 2017, 2016 and 2015, respectively. Management has concluded that the error was not material to any period presented. In addition, a discrete tax benefit of $52 million was recorded in the first nine months of 2018, compared to $45 million in the first nine months of 2017, for the settlement of stock-based compensation awards with associated tax deductions in excess of cumulative U.S. GAAP compensation expense. The provision for income taxes for the first nine months of 2018 also included a $25 million benefit for the release of a valuation allowance against the deferred tax assets of a non-U.S. subsidiary. The provision for income taxes for the first nine months of 2017 also included a $15 million increase to prior year taxes related to non-U.S. restructuring costs.

Our analysis of U.S. tax reform legislation, updated through September 30, 2018, resulted in no other changes to the 2017 year-end provisional charge. We will continue to update our calculations as additional required information is prepared and analyzed, interpretations and assumptions are refined, and additional guidance is issued. These updates could significantly impact the provision for income taxes, the amount of taxes payable and the deferred tax asset and liability balances. We account for the new U.S. tax on global intangible low-taxed income as a period cost.

On January 31, 2018, we received a Revenue Agent's Report from the Internal Revenue Service (IRS) indicating the end of the field examination of our U.S. income tax returns for 2010 to 2012. In the audits of 2007 to 2012 including the impact of a loss carryback to 2005, the IRS has proposed to tax in the United States profits earned from certain parts transactions by Caterpillar SARL, based on the IRS examination team's application of the "substance-over-form" or "assignment-of-income" judicial doctrines. We are vigorously contesting the proposed increases to tax and penalties for these years of approximately $2.3 billion. We believe that the relevant transactions complied with applicable tax laws and did not violate judicial doctrines. We have filed U.S. income tax returns on this same basis for years after 2012. Based on the information currently available, we do not anticipate a significant increase or decrease to our unrecognized tax benefits for this matter within the next 12 months. We currently believe the ultimate disposition of this matter will not have a material adverse effect on our consolidated financial position, liquidity or results of operations.