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Income Taxes - Schedule of Deferred Income Tax Components (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Income Taxes [Line Items] |  |  |
Net change in deferred income tax liability per above table | $ (393,440) |  |
Change in tax effects of income tax related regulatory assets and liabilities | (16,444) |  |
Tax effect of mark-to-market adjustments | (4,724) |  |
Tax effect of excess pension liability | (3,421) |  |
Adjustment for uncertain income tax positions | 2,677 |  |
Reclassification of unrecognized tax benefits | (2,677) |  |
Regulatory recovery of prior year impairments of state net operating loss carryforward, net of amortization | (2,225) |  |
Federal income tax rate change | 548,952 |  |
Cumulative effect adjustment for excess tax benefit related to stock compensation awards | 10,382 |  |
Alternative minimum tax carryforward reclassified to receivable | (8,336) |  |
Other | (216) |  |
Deferred income taxes | 130,528 | $ 63,805 | $ 16,451
Public Service Company of New Mexico |  |  |
Income Taxes [Line Items] |  |  |
Net change in deferred income tax liability per above table | (299,654) |  |
Change in tax effects of income tax related regulatory assets and liabilities | (16,332) |  |
Tax effect of mark-to-market adjustments | (4,110) |  |
Tax effect of excess pension liability | (3,421) |  |
Adjustment for uncertain income tax positions | 2,614 |  |
Reclassification of unrecognized tax benefits | (2,614) |  |
Regulatory recovery of prior year impairments of state net operating loss carryforward, net of amortization | (2,225) |  |
Federal income tax rate change | 402,501 |  |
Cumulative effect adjustment for excess tax benefit related to stock compensation awards | 7,770 |  |
Other | (1,980) |  |
Deferred income taxes | 82,549 | 53,119 | (2,836)
Texas-New Mexico Power Company |  |  |
Income Taxes [Line Items] |  |  |
Net change in deferred income tax liability per above table | (119,370) |  |
Change in tax effects of income tax related regulatory assets and liabilities | (112) |  |
Federal income tax rate change | 146,451 |  |
Other | 306 |  |
Deferred income taxes | $ 27,275 | $ 12,662 | $ 20,883

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