Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The increase in income tax expense between quarterly periods of $971 million, from $672 million in 2017 to $1.64 billion in 2018, is a result of the year-over-year increase in total income before income tax expense, which is primarily due to effects of higher crude oil prices and higher production. The company’s effective tax rate changed between periods from 25 percent in 2017 to 29 percent in 2018. The change in effective tax rate is primarily a consequence of the mix effect resulting from the absolute level of earnings or losses and whether they arose in higher or lower tax rate jurisdictions. The increase in income tax expense for the nine months of $2.95 billion, from $1.59 billion in 2017 to $4.54 billion in 2018, is a result of the year-over-year increase in total income before income tax expense, which is primarily due to effects of higher crude oil prices and higher production. The company’s effective tax rate changed between periods from 21 percent in 2017 to 29 percent in 2018. The change in effective tax rate is primarily a consequence of the mix effect resulting from the absolute level of earnings or losses and whether they arose in higher or lower tax rate jurisdictions. U.S. tax reform resulted in the remeasurement of U.S. deferred tax assets and liabilities in 2017. The company's U.S. tax return was prepared and filed in the quarter ended September 30, 2018, and did not result in any material change to the provisional amounts that were recognized in 2017. Further proposed regulations are expected to be issued later in 2018 which may result in a change to the provisional amounts that were recognized in 2017. Tax positions for Chevron and its subsidiaries and affiliates are subject to income tax audits by many tax jurisdictions throughout the world. For the company’s major tax jurisdictions, examinations of tax returns for certain prior tax years had not been completed as of September 30, 2018. For these jurisdictions, the latest years for which income tax examinations had been finalized were as follows: United States — 2011, Nigeria — 2000, Australia — 2006 and Kazakhstan — 2007. The company engages in ongoing discussions with tax authorities regarding the resolution of tax matters in the various jurisdictions. Both the outcomes for these tax matters and the timing of resolution and/or closure of the tax audits are highly uncertain. However, it is reasonably possible that developments regarding tax matters in certain tax jurisdictions may result in significant increases or decreases in the company’s total unrecognized tax benefits within the next 12 months. Given the number of years that still remain subject to examination and the number of matters being examined in the various tax jurisdictions, the company is unable to estimate the range of possible adjustments to the balance of unrecognized tax benefits.

Income Taxes

The increase in income tax expense between quarterly periods of $971 million, from $672 million in 2017 to $1.64 billion in 2018, is a result of the year-over-year increase in total income before income tax expense, which is primarily due to effects of higher crude oil prices and higher production. The company’s effective tax rate changed between periods from 25 percent in 2017 to 29 percent in 2018. The change in effective tax rate is primarily a consequence of the mix effect resulting from the absolute level of earnings or losses and whether they arose in higher or lower tax rate jurisdictions.

The increase in income tax expense for the nine months of $2.95 billion, from $1.59 billion in 2017 to $4.54 billion in 2018, is a result of the year-over-year increase in total income before income tax expense, which is primarily due to effects of higher crude oil prices and higher production. The company’s effective tax rate changed between periods from 21 percent in 2017 to 29 percent in 2018. The change in effective tax rate is primarily a consequence of the mix effect resulting from the absolute level of earnings or losses and whether they arose in higher or lower tax rate jurisdictions.

U.S. tax reform resulted in the remeasurement of U.S. deferred tax assets and liabilities in 2017. The company's U.S. tax return was prepared and filed in the quarter ended September 30, 2018, and did not result in any material change to the provisional amounts that were recognized in 2017. Further proposed regulations are expected to be issued later in 2018 which may result in a change to the provisional amounts that were recognized in 2017.

Tax positions for Chevron and its subsidiaries and affiliates are subject to income tax audits by many tax jurisdictions throughout the world. For the company’s major tax jurisdictions, examinations of tax returns for certain prior tax years had not been completed as of September 30, 2018. For these jurisdictions, the latest years for which income tax examinations had been finalized were as follows: United States — 2011, Nigeria — 2000, Australia — 2006 and Kazakhstan — 2007.

The company engages in ongoing discussions with tax authorities regarding the resolution of tax matters in the various jurisdictions. Both the outcomes for these tax matters and the timing of resolution and/or closure of the tax audits are highly uncertain. However, it is reasonably possible that developments regarding tax matters in certain tax jurisdictions may result in significant increases or decreases in the company’s total unrecognized tax benefits within the next 12 months. Given the number of years that still remain subject to examination and the number of matters being examined in the various tax jurisdictions, the company is unable to estimate the range of possible adjustments to the balance of unrecognized tax benefits.