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Financing - Long-term Debt (Details) - USD ($) | Dec. 31, 2015 | Aug. 11, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Apr. 03, 2013 | Mar. 06, 2013
--- | --- | --- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |  |  |
Total | $ 2,086,370,000 |  | $ 1,955,136,000 |  |  |
Long-term debt, Current maturities, Gross | 125,000,000 |  | 333,066,000 |  |  |
Long-term debt, Excluding current maturities, Gross | 1,961,370,000 |  | 1,622,070,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | (5,578,000) |  | (7,249,000) |  |  |
Unamortized Amounts, net, less current maturities | 21,000 |  | 195,000 |  |  |
Unamortized Amounts, net, excluding current maturities | (5,599,000) |  | (7,444,000) |  |  |
Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt issuance expense, current portion, reclassified |  |  | 0 |  |  |
Debt issuance expense, long-term portion, reclassified |  |  | 200,000 |  |  |
Unsecured Debt [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Stated percentage |  |  |  | 9.25% |  |
Unsecured Debt [Member] | Senior unsecured notes, 9.25% due 2015 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent |  |  | $ 118,800,000 |  |  |
Stated percentage |  |  | 9.25% |  |  |
Public Service Company of New Mexico [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Total | 1,590,870,000 |  | $ 1,490,870,000 |  |  |
Long-term debt, Current maturities, Gross | 125,000,000 |  | 214,300,000 |  |  |
Long-term debt, Excluding current maturities, Gross | 1,465,870,000 |  | 1,276,570,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 10,193,000 |  | 8,333,000 |  |  |
Unamortized Amounts, net, less current maturities | 21,000 |  | 36,000 |  |  |
Unamortized Amounts, net, excluding current maturities | 10,172,000 |  | 8,297,000 |  |  |
Public Service Company of New Mexico [Member] | Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt issuance expense, current portion, reclassified |  |  | 100,000 |  |  |
Debt issuance expense, long-term portion, reclassified |  |  | 8,100,000 |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 4.875% due 2033 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | 146,000,000 |  | 146,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 721,000 |  | $ 807,000 |  |  |
Stated percentage | 4.875% |  | 4.875% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 6.25% due 2038 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 36,000,000 |  | $ 36,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 251,000 |  | $ 262,000 |  |  |
Stated percentage | 6.25% |  | 6.25% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 4.75% due 2040, mandatory tender at June 1, 2017 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 37,000,000 |  | $ 37,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 82,000 |  | $ 138,000 |  |  |
Stated percentage | 4.75% |  | 4.75% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 5.20% due 2040, mandatory tender at June 1, 2020 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 40,045,000 |  | $ 40,045,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 190,000 |  | $ 233,000 |  |  |
Stated percentage | 5.20% |  | 5.20% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 5.90% due 2040 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 255,000,000 |  | $ 255,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 2,222,000 |  | $ 2,313,000 |  |  |
Stated percentage | 5.90% |  | 5.90% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 6.25% due 2040 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 11,500,000 |  | $ 11,500,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 100,000 |  | $ 104,000 |  |  |
Stated percentage | 6.25% |  | 6.25% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 2.54% due 2042, mandatory tender at June 1, 2017 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 20,000,000 |  | $ 20,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 199,000 |  | $ 331,000 |  |  |
Stated percentage | 2.54% |  | 2.54% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 4.00% due 2043, mandatory tender at June 1, 2015 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 0 |  | $ 39,300,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 |  | $ 36,000 |  |  |
Stated percentage | 0.00% |  | 4.00% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 2.40% due 2043, mandatory tender at June 1, 2020 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 39,300,000 |  | $ 0 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 456,000 |  | $ 0 |  |  |
Stated percentage | 2.40% |  | 0.00% |  |  |
Public Service Company of New Mexico [Member] | Senior Unsecured Notes, Pollution Control Revenue Bonds [Member] | 5.20% due 2043, mandatory tender at June 1, 2020 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 21,000,000 |  | $ 21,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 96,000 |  | $ 118,000 |  |  |
Stated percentage | 5.20% |  | 5.20% |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | 7.95% due 2018 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 350,000,000 |  | $ 350,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 1,718,000 |  | $ 2,441,000 |  |  |
Stated percentage | 7.95% |  | 7.95% |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | 7.50% due 2018 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 100,025,000 |  | $ 100,025,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 320,000 |  | $ 444,000 |  |  |
Stated percentage | 7.50% |  | 7.50% |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | 5.35% due 2021 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 160,000,000 |  | $ 160,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 943,000 |  | $ 1,106,000 |  |  |
Stated percentage | 5.35% |  | 5.35% |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | 3.85% due 2025 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 250,000,000 | $ 250,000,000.0 | $ 0 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 2,874,000 |  | $ 0 |  |  |
Stated percentage | 3.85% | 3.85% | 3.85% |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | PNM Term Loan Agreement due 2015 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Long-term debt | $ 0 |  | $ 175,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 0 |  | 0 |  |  |
Public Service Company of New Mexico [Member] | Unsecured Debt [Member] | PNM Multi-Draw Term Loan Agreement due 2016 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Long-term debt | 125,000,000 |  | 100,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 21,000 |  | 0 |  |  |
Texas-New Mexico Power Company [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Total | 345,500,000 |  | 345,500,000 |  |  |
Long-term debt, Current maturities, Gross | 0 |  | 0 |  |  |
Long-term debt, Excluding current maturities, Gross | 345,500,000 |  | 345,500,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | (15,911,000) |  | (15,741,000) |  |  |
Unamortized Amounts, net, less current maturities | 0 |  | 0 |  |  |
Unamortized Amounts, net, excluding current maturities | (15,911,000) |  | (15,741,000) |  |  |
Texas-New Mexico Power Company [Member] | Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Debt issuance expense, current portion, reclassified |  |  | 0 |  |  |
Debt issuance expense, long-term portion, reclassified |  |  | 4,400,000 |  |  |
Texas-New Mexico Power Company [Member] | First Mortgage Bonds [Member] | First Mortgage Bonds Due 2014, Series 2009A, at 9.50% [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | 172,302,000 |  | 172,302,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 2,682,000 |  | $ 3,508,000 |  |  |
Stated percentage | 9.50% |  | 9.50% |  | 9.50% | 9.50%
Texas-New Mexico Power Company [Member] | First Mortgage Bonds [Member] | First Mortgage Bonds 6.95%, due 2043, Series 2013A [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 93,198,000 |  | $ 93,198,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ (19,490,000) |  | $ (20,208,000) |  |  |
Stated percentage | 6.95% |  | 6.95% |  | 6.95% | 6.95%
Texas-New Mexico Power Company [Member] | First Mortgage Bonds [Member] | First Mortgage Bonds Due 2024, Series 2014A, at 4.03% [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | $ 80,000,000 |  | $ 80,000,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 897,000 |  | $ 959,000 |  |  |
Stated percentage | 4.03% |  | 4.03% |  |  |
PNMR [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Total | $ 150,000,000 |  | $ 118,766,000 |  |  |
Long-term debt, Current maturities, Gross | 0 |  | 118,766,000 |  |  |
Long-term debt, Excluding current maturities, Gross | 150,000,000 |  | 0 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 140,000 |  | 159,000 |  |  |
Unamortized Amounts, net, less current maturities | 0 |  | 159,000 |  |  |
Unamortized Amounts, net, excluding current maturities | 140,000 |  | 0 |  |  |
PNMR [Member] | Unsecured Debt [Member] | PNMR Term Loan Agreement due 2018 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Long-term debt | 150,000,000 |  | 0 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | 140,000 |  | 0 |  |  |
PNMR [Member] | Unsecured Debt [Member] | Senior unsecured notes, 9.25% due 2015 [Member] |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Unsecured long-term debt, noncurrent | 0 |  | 118,766,000 |  |  |
Unamortized Discounts, (Premiums), and Issuance Costs, net | $ 0 |  | $ 159,000 |  |  |
Stated percentage | 0.00% |  | 9.25% |  |  |

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