Income Taxes	9 Months Ended
Sep. 30, 2017
Income Taxes
Income Taxes	4. Income Taxes Our effective income tax rate for the three and nine months ended September 30, 2017 was 35.7% and 34.9%, respectively, compared with 33.7% and 35.5%, respectively, for the comparable prior year periods. We evaluate our effective income tax rate at each interim period and adjust it as facts and circumstances warrant. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the three months ended September 30, 2017 was primarily due to the unfavorable impact of state and local income taxes offset, in part, by the favorable impact of federal tax credits and adjustments to our accruals and related deferred taxes due to the filing of our 2016 income tax returns. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the nine months ended September 30, 2017 was primarily due to the favorable impact of federal tax credits, excess tax benefits related to equity-based compensation and adjustments to our accruals and related deferred taxes due to the filing of our 2016 income tax returns offset, in part, by the unfavorable impact of state and local income taxes and nondeductible impairments. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the three months ended September 30, 2016 was primarily due to the favorable impact of federal tax credits and adjustments to our accruals and related deferred taxes due to the filing of our 2015 income tax returns offset, in part, by the unfavorable impact of state and local income taxes and nondeductible impairments and capital losses. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the nine months ended September 30, 2016 was primarily due to the unfavorable impact of state and local income taxes and nondeductible impairments and capital losses offset, in part, by the favorable impact of federal tax credits, adjustments to our accruals and related deferred taxes due to the filing of our 2015 income tax returns, and tax audit settlements. Equity-Based Compensation — During the three and nine months ended September 30, 2017, we recognized a reduction in our income tax expense of $1 million and $35 million, respectively, for excess tax benefits related to the vesting or exercise of equity-based compensation awards. See Note 1 for discussion of our adoption of ASU 2016‑09. Investments Qualifying for Federal Tax Credits — We have significant financial interests in entities established to invest in and manage low-income housing properties and a refined coal facility. We support the operations of these entities in exchange for a pro-rata share of the tax credits they generate. The low-income housing investments and the coal facility’s refinement processes qualify for federal tax credits that we expect to realize through 2020 under Section 42 and through 2019 under Section 45, respectively, of the Internal Revenue Code. We account for our investments in these entities using the equity method of accounting, recognizing our share of each entity’s results of operations and other reductions in the value of our investments in equity in net losses of unconsolidated entities, within our Condensed Consolidated Statements of Operations. During the three and nine months ended September 30, 2017, we recognized $6 million and $21 million of net losses and a reduction in our income tax expense of $14 million and $39 million, respectively, primarily because of tax credits realized from these investments. During the three and nine months ended September 30, 2016, we recognized $7 million and $22 million of net losses and a reduction in our income tax expense of $15 million and $40 million, respectively, primarily because of tax credits realized from these investments. Interest expense associated with our investment in low-income housing properties was not material for the periods presented. See Note 13 for additional information related to these unconsolidated variable interest entities.

4. Income Taxes

Our effective income tax rate for the three and nine months ended September 30, 2017 was 35.7% and 34.9%, respectively, compared with 33.7% and 35.5%, respectively, for the comparable prior year periods. We evaluate our effective income tax rate at each interim period and adjust it as facts and circumstances warrant. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the three months ended September 30, 2017 was primarily due to the unfavorable impact of state and local income taxes offset, in part, by the favorable impact of federal tax credits and adjustments to our accruals and related deferred taxes due to the filing of our 2016 income tax returns. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the nine months ended September 30, 2017 was primarily due to the favorable impact of federal tax credits, excess tax benefits related to equity-based compensation and adjustments to our accruals and related deferred taxes due to the filing of our 2016 income tax returns offset, in part, by the unfavorable impact of state and local income taxes and nondeductible impairments.

The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the three months ended September 30, 2016 was primarily due to the favorable impact of federal tax credits and adjustments to our accruals and related deferred taxes due to the filing of our 2015 income tax returns offset, in part, by the unfavorable impact of state and local income taxes and nondeductible impairments and capital losses. The difference between federal income taxes computed at the federal statutory rate and reported income taxes for the nine months ended September 30, 2016 was primarily due to the unfavorable impact of state and local income taxes and nondeductible impairments and capital losses offset, in part, by the favorable impact of federal tax credits, adjustments to our accruals and related deferred taxes due to the filing of our 2015 income tax returns, and tax audit settlements.

Equity-Based Compensation — During the three and nine months ended September 30, 2017, we recognized a reduction in our income tax expense of $1 million and $35 million, respectively, for excess tax benefits related to the vesting or exercise of equity-based compensation awards. See Note 1 for discussion of our adoption of ASU 2016‑09.

Investments Qualifying for Federal Tax Credits — We have significant financial interests in entities established to invest in and manage low-income housing properties and a refined coal facility. We support the operations of these entities in exchange for a pro-rata share of the tax credits they generate. The low-income housing investments and the coal facility’s refinement processes qualify for federal tax credits that we expect to realize through 2020 under Section 42 and through 2019 under Section 45, respectively, of the Internal Revenue Code.

We account for our investments in these entities using the equity method of accounting, recognizing our share of each entity’s results of operations and other reductions in the value of our investments in equity in net losses of unconsolidated entities, within our Condensed Consolidated Statements of Operations. During the three and nine months ended September 30, 2017, we recognized $6 million and $21 million of net losses and a reduction in our income tax expense of $14 million and $39 million, respectively, primarily because of tax credits realized from these investments. During the three and nine months ended September 30, 2016, we recognized $7 million and $22 million of net losses and a reduction in our income tax expense of $15 million and $40 million, respectively, primarily because of tax credits realized from these investments. Interest expense associated with our investment in low-income housing properties was not material for the periods presented. See Note 13 for additional information related to these unconsolidated variable interest entities.