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Income Taxes - Interest Income (Expense) Related to Income Taxes (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Income Taxes [Line Items] |  |  |
Interest income related to income taxes | $ 0 | $ 4,398 | $ 0
Public Service Company of New Mexico |  |  |
Income Taxes [Line Items] |  |  |
Interest income related to income taxes | 0 | 3,625 | 0
Texas-New Mexico Power Company |  |  |
Income Taxes [Line Items] |  |  |
Interest income related to income taxes | $ 0 | 345 | $ 0
Interest income and interest expense applicable to federal income tax matters |  |  |
Income Taxes [Line Items] |  |  |
Net refunds received |  | 6,500 |
Increase (decrease) of net interest receivable |  | (2,100) |
Interest income |  | 5,100 |
Interest expense |  | 700 |
Professional fees |  | 900 |
Net pre-tax impacts |  | 3,500 |
Interest income and interest expense applicable to federal income tax matters | Public Service Company of New Mexico |  |  |
Income Taxes [Line Items] |  |  |
Net pre-tax impacts |  | 2,600 |
Interest income and interest expense applicable to federal income tax matters | Texas-New Mexico Power Company |  |  |
Income Taxes [Line Items] |  |  |
Net pre-tax impacts |  | 300 |
Interest income and interest expense applicable to federal income tax matters | Corporate and Other |  |  |
Income Taxes [Line Items] |  |  |
Net pre-tax impacts |  | $ 600 |

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- Definition The increase (decrease) during the reporting period in the aggregate amount due to the entity in the form of unpaid interest and dividends. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 + Details
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- Definition Amount of interest expense classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4D -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph -4 -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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- Definition The amount of cash received during the period as refunds for the overpayment of taxes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586 + Details
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