Income Taxes	9 Months Ended
Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In 2013, New Mexico House Bill 641 reduced the New Mexico corporate income tax rate from 7.6% to 5.9%. The rate reduction is being phased-in from 2014 to 2018. In accordance with GAAP, PNMR and PNM adjusted accumulated deferred income taxes during the period that includes the date of enactment, which was in the year ended December 31, 2013, to reflect the tax rate at which the balances are expected to reverse. At that time, the portion of the adjustment related to PNM’s regulated activities was recorded as a reduction in deferred tax liabilities, which was offset by an increase in a regulatory liability, on the assumption that PNM would be required to return the benefit to customers over time. In addition, the portion of the adjustment that is not related to PNM’s regulated activities was recorded in PNMR’s Corporate and Other segment as a reduction in deferred tax assets and an increase in income tax expense. Changes in the estimated timing of reversals of deferred tax assets and liabilities will result in refinements of the impacts of this change in tax rates being recorded periodically until 2018, when the rate reduction is fully phased in. In the three months ended March 31, 2017 and 2016, PNM’s regulatory liability was reduced by $4.8 million and $7.1 million, which increased deferred tax liabilities. Deferred tax assets not related to PNM’s regulatory activities were: reduced by $0.1 million in the three months ended March 31, 2017, increasing income tax expense by less than $0.1 million for PNM and $0.1 million for the Corporate and Other segment; and decreased by $0.7 million in the three months ended March 31, 2016, increasing income tax expense by $0.8 million for PNM and reducing income tax expense by $0.1 million for the Corporate and Other segment. In the stipulation filed in PNM’s NM 2016 Rate Case (Note 12), it is proposed that the benefit of the lower New Mexico corporate income tax rate be returned to customers over a three-year period beginning January 1, 2018. In 2008, fifty percent bonus tax depreciation was enacted as a temporary two-year stimulus measure as part of the Economic Stimulus Act of 2008. Bonus tax depreciation in various forms has been continuously extended since that time. As a result of the net operating loss carryforwards for income tax purposes created by bonus depreciation, and reduced future income taxes payable resulting from New Mexico House Bill 641, certain tax carryforwards are not expected to be utilized before their expiration. In accordance with GAAP, PNMR and PNM have impaired the tax carryforwards which were not expected to be utilized prior to their expiration. The Company has not recorded any impairments in 2016 or 2017. The NMPRC’s final order in PNM’s NM 2015 Rate Case (Note 12) approved PNM’s request to record a regulatory asset to recover a 2014 impairment of PNM’s New Mexico net operating loss carryforward resulting from the extension of bonus depreciation. The impact, net of federal income taxes, amounts to $2.1 million, which is reflected as a reduction of income tax expense on the Condensed Consolidated Statement of Earnings in the three months ended September 30, 2016. The Company undertook an analysis of interest income and interest expense applicable to federal income tax matters. The analysis encompassed the impacts of IRS examinations, amended income tax returns, and filings for carrybacks of tax matters to previous taxable years applicable to all years not closed under the IRS rules. As a result of this effort, PNMR received net refunds from the IRS of $6.5 million in the three months ended June 30, 2016. Of the refunds, $2.1 million was recorded as a reduction of interest receivable and $5.1 million was recorded as interest income, which was partially offset by $0.7 million of interest expense. In addition, PNMR incurred $0.9 million in professional fees related to the analysis. Of the net pre-tax impacts aggregating $3.5 million, $2.6 million is reflected in the PNM segment, $0.3 million in the TNMP segment, and $0.6 million in the Corporate and Other segment. See Note 8 for a discussion of the impacts on income tax expense resulting from the adoption of Accounting Standards Update 2016-09 – Compensation –- Stock Compensation (Topic 718).

Income Taxes

In 2013, New Mexico House Bill 641 reduced the New Mexico corporate income tax rate from 7.6% to 5.9%. The rate reduction is being phased-in from 2014 to 2018. In accordance with GAAP, PNMR and PNM adjusted accumulated deferred income taxes during the period that includes the date of enactment, which was in the year ended December 31, 2013, to reflect the tax rate at which the balances are expected to reverse. At that time, the portion of the adjustment related to PNM’s regulated activities was recorded as a reduction in deferred tax liabilities, which was offset by an increase in a regulatory liability, on the assumption that PNM would be required to return the benefit to customers over time. In addition, the portion of the adjustment that is not related to PNM’s regulated activities was recorded in PNMR’s Corporate and Other segment as a reduction in deferred tax assets and an increase in income tax expense. Changes in the estimated timing of reversals of deferred tax assets and liabilities will result in refinements of the impacts of this change in tax rates being recorded periodically until 2018, when the rate reduction is fully phased in. In the three months ended March 31, 2017 and 2016, PNM’s regulatory liability was reduced by $4.8 million and $7.1 million, which increased deferred tax liabilities. Deferred tax assets not related to PNM’s regulatory activities were: reduced by $0.1 million in the three months ended March 31, 2017, increasing income tax expense by less than $0.1 million for PNM and $0.1 million for the Corporate and Other segment; and decreased by $0.7 million in the three months ended March 31, 2016, increasing income tax expense by $0.8 million for PNM and reducing income tax expense by $0.1 million for the Corporate and Other segment. In the stipulation filed in PNM’s NM 2016 Rate Case (Note 12), it is proposed that the benefit of the lower New Mexico corporate income tax rate be returned to customers over a three-year period beginning January 1, 2018.

In 2008, fifty percent bonus tax depreciation was enacted as a temporary two-year stimulus measure as part of the Economic Stimulus Act of 2008. Bonus tax depreciation in various forms has been continuously extended since that time. As a result of the net operating loss carryforwards for income tax purposes created by bonus depreciation, and reduced future income taxes payable resulting from New Mexico House Bill 641, certain tax carryforwards are not expected to be utilized before their expiration. In accordance with GAAP, PNMR and PNM have impaired the tax carryforwards which were not expected to be utilized prior to their expiration. The Company has not recorded any impairments in 2016 or 2017. The NMPRC’s final order in PNM’s NM 2015 Rate Case (Note 12) approved PNM’s request to record a regulatory asset to recover a 2014 impairment of PNM’s New Mexico net operating loss carryforward resulting from the extension of bonus depreciation. The impact, net of federal income taxes, amounts to $2.1 million, which is reflected as a reduction of income tax expense on the Condensed Consolidated Statement of Earnings in the three months ended September 30, 2016.

The Company undertook an analysis of interest income and interest expense applicable to federal income tax matters. The analysis encompassed the impacts of IRS examinations, amended income tax returns, and filings for carrybacks of tax matters to previous taxable years applicable to all years not closed under the IRS rules. As a result of this effort, PNMR received net refunds from the IRS of $6.5 million in the three months ended June 30, 2016. Of the refunds, $2.1 million was recorded as a reduction of interest receivable and $5.1 million was recorded as interest income, which was partially offset by $0.7 million of interest expense. In addition, PNMR incurred $0.9 million in professional fees related to the analysis. Of the net pre-tax impacts aggregating $3.5 million, $2.6 million is reflected in the PNM segment, $0.3 million in the TNMP segment, and $0.6 million in the Corporate and Other segment.

See Note 8 for a discussion of the impacts on income tax expense resulting from the adoption of Accounting Standards Update 2016-09 – Compensation –- Stock Compensation (Topic 718).