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Segment Information - Summarized Financial Information (Details) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) segment | Sep. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items] |  |  |  |  |
Number of operating segments | segment |  |  | 1 |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Electric operating revenues | $ 422,666 | $ 419,900 | $ 1,092,857 | $ 1,112,398 |
Utility margin | 309,130 | 316,152 | 799,054 | 801,580 |
Other operating expenses | 119,560 | 112,709 | 365,238 | 338,788 |
Depreciation and amortization | 61,580 | 58,821 | 180,365 | 172,829 |
Operating income | 127,990 | 144,622 | 253,451 | 289,963 |
Interest income | 3,400 | 3,582 | 11,862 | 12,348 |
Other income (deductions) | 3,574 | 4,972 | 3,214 | 14,984 |
Interest charges | (30,492) | (32,106) | (96,868) | (96,137) |
Earnings before Income Taxes | 104,472 | 121,070 | 171,659 | 221,158 |
Income taxes (benefit) | 12,899 | 42,743 | 18,838 | 75,154 |
Net Earnings | 91,573 | 78,327 | 152,821 | 146,004 |
Valencia non-controlling interest | (3,920) | (4,456) | (11,706) | (11,452) |
Subsidiary preferred stock dividends | (132) | (132) | (396) | (396) |
Net Earnings Available for PNM Common Stock | 87,521 | 73,739 | 140,719 | 134,156 |
Total Assets | 6,848,995 | 6,697,254 | 6,848,995 | 6,697,254 | $ 6,646,103
Goodwill | 278,297 | 278,297 | 278,297 | 278,297 | $ 278,297
PNM |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Utility margin | 238,990 | 244,887 | 602,569 | 608,274 |
Other operating expenses | 98,000 | 92,733 | 305,569 | 281,886 |
Depreciation and amortization | 38,474 | 36,764 | 113,314 | 109,228 |
Operating income | 102,516 | 115,390 | 183,686 | 217,160 |
Interest income | 3,472 | 1,782 | 9,340 | 6,457 |
Other income (deductions) | 2,515 | 4,204 | 588 | 13,510 |
Interest charges | (18,063) | (20,451) | (58,881) | (62,393) |
Earnings before Income Taxes | 90,440 | 100,925 | 134,733 | 174,734 |
Income taxes (benefit) | 9,012 | 35,642 | 11,009 | 58,865 |
Net Earnings | 81,428 | 65,283 | 123,724 | 115,869 |
Valencia non-controlling interest | (3,920) | (4,456) | (11,706) | (11,452) |
Subsidiary preferred stock dividends | (132) | (132) | (396) | (396) |
Net Earnings Available for PNM Common Stock | 77,376 | 60,695 | 111,622 | 104,021 |
Total Assets | 5,042,761 | 5,023,816 | 5,042,761 | 5,023,816 |
Goodwill | 51,632 | 51,632 | 51,632 | 51,632 |
TNMP |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Utility margin | 70,140 | 71,265 | 196,485 | 193,306 |
Other operating expenses | 25,140 | 25,367 | 73,624 | 72,188 |
Depreciation and amortization | 17,176 | 16,424 | 49,676 | 47,392 |
Operating income | 27,824 | 29,474 | 73,185 | 73,726 |
Interest income | 0 | 0 | 0 | 0 |
Other income (deductions) | 1,151 | 1,228 | 3,067 | 2,392 |
Interest charges | (8,241) | (7,704) | (23,771) | (22,619) |
Earnings before Income Taxes | 20,734 | 22,998 | 52,481 | 53,499 |
Income taxes (benefit) | 4,634 | 8,271 | 11,602 | 18,964 |
Net Earnings | 16,100 | 14,727 | 40,879 | 34,535 |
Valencia non-controlling interest | 0 | 0 | 0 | 0 |
Subsidiary preferred stock dividends | 0 | 0 | 0 | 0 |
Net Earnings Available for PNM Common Stock | 16,100 | 14,727 | 40,879 | 34,535 |
Total Assets | 1,628,842 | 1,465,219 | 1,628,842 | 1,465,219 |
Goodwill | 226,665 | 226,665 | 226,665 | 226,665 |
Corporate and Other |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Utility margin | 0 | 0 | 0 | 0 |
Other operating expenses | (3,580) | (5,391) | (13,955) | (15,286) |
Depreciation and amortization | 5,930 | 5,633 | 17,375 | 16,209 |
Operating income | (2,350) | (242) | (3,420) | (923) |
Interest income | (72) | 1,800 | 2,522 | 5,891 |
Other income (deductions) | (92) | (460) | (441) | (918) |
Interest charges | (4,188) | (3,951) | (14,216) | (11,125) |
Earnings before Income Taxes | (6,702) | (2,853) | (15,555) | (7,075) |
Income taxes (benefit) | (747) | (1,170) | (3,773) | (2,675) |
Net Earnings | (5,955) | (1,683) | (11,782) | (4,400) |
Valencia non-controlling interest | 0 | 0 | 0 | 0 |
Subsidiary preferred stock dividends | 0 | 0 | 0 | 0 |
Net Earnings Available for PNM Common Stock | (5,955) | (1,683) | (11,782) | (4,400) |
Total Assets | 177,392 | 208,219 | 177,392 | 208,219 |
Goodwill | 0 | 0 | 0 | 0 |
Electricity |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Electric operating revenues | 422,666 | 419,900 | 1,092,857 | 1,112,398 |
Cost of energy | 113,536 | 103,748 | 293,803 | 310,818 |
Electricity | PNM |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Electric operating revenues | 331,374 | 327,254 | 832,116 | 854,909 |
Cost of energy | 92,384 | 82,367 | 229,547 | 246,635 |
Electricity | TNMP |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Electric operating revenues | 91,292 | 92,646 | 260,741 | 257,489 |
Cost of energy | 21,152 | 21,381 | 64,256 | 64,183 |
Electricity | Corporate and Other |  |  |  |  |
Segment Reporting Information, Profit (Loss) [Abstract] |  |  |  |  |
Electric operating revenues | 0 | 0 | 0 | 0 |
Cost of energy | $ 0 | $ 0 | $ 0 | $ 0 |

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Data Type: | na
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