Income Taxes	9 Months Ended
Sep. 30, 2018
Income Taxes
Income Taxes	8. Income Taxes Our effective income tax rates for the three-month periods ended September 30, 2018 and 2017 were 22.9% and 30.4%, respectively. Our effective income tax rates for the nine-month periods ended September 30, 2018 and 2017 were 23.7% and 31.5%, respectively. Our 2018 three-month and nine-month period effective income tax rates were favorably impacted by the Tax Cuts and Jobs Act of 2017 (“Tax Reform”), which included significant changes to the taxation of U.S. corporations, including a reduction of the U.S. federal statutory rate from 35% to 21%, effective January 1, 2018. Based on our preliminary assessment of the impact of Tax Reform, we recognized a one-time, provisional net tax benefit of $207.3 million in the fourth quarter of 2017, primarily related to the remeasurement of deferred tax assets and liabilities at the lowered federal statutory tax rate, which was partially offset by repatriation and related liabilities. Given the substantial changes to the Internal Revenue Code as a result of Tax Reform, our estimates of the financial impacts attributable to Tax Reform are subject to continuing analysis, interpretation and clarification of the new law, which could result in changes to our estimates in the fourth quarter of 2018. The adjustments to our provisional estimates during the nine months ended September 30, 2018 were not significant. State income taxes offset by the effects of company-owned life insurance policies mainly accounted for the difference between our effective income tax rate and the federal statutory rate for the nine months ended September 30, 2018.

8. Income Taxes

Our effective income tax rates for the three-month periods ended September 30, 2018 and 2017 were 22.9% and 30.4%, respectively. Our effective income tax rates for the nine-month periods ended September 30, 2018 and 2017 were 23.7% and 31.5%, respectively. Our 2018 three-month and nine-month period effective income tax rates were favorably impacted by the Tax Cuts and Jobs Act of 2017 (“Tax Reform”), which included significant changes to the taxation of U.S. corporations, including a reduction of the U.S. federal statutory rate from 35% to 21%, effective January 1, 2018. Based on our preliminary assessment of the impact of Tax Reform, we recognized a one-time, provisional net tax benefit of $207.3 million in the fourth quarter of 2017, primarily related to the remeasurement of deferred tax assets and liabilities at the lowered federal statutory tax rate, which was partially offset by repatriation and related liabilities. Given the substantial changes to the Internal Revenue Code as a result of Tax Reform, our estimates of the financial impacts attributable to Tax Reform are subject to continuing analysis, interpretation and clarification of the new law, which could result in changes to our estimates in the fourth quarter of 2018. The adjustments to our provisional estimates during the nine months ended September 30, 2018 were not significant. State income taxes offset by the effects of company-owned life insurance policies mainly accounted for the difference between our effective income tax rate and the federal statutory rate for the nine months ended September 30, 2018.