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Fair Value of Derivative and Other Financial Instruments - Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Public Service Company of New Mexico [Member] | Pension Plan [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | $ 557,923 | $ 587,909
Fair value of plan assets at end of year | 543,601 | 557,923
Public Service Company of New Mexico [Member] | Pension Plan [Member] | PNMR Master Trust [Member] | Fair Value Measurement [Domain] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 479,858 |
Fair value of plan assets at end of year | 467,965 | 479,858
Public Service Company of New Mexico [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 558,319 |
Fair value of plan assets at end of year | 543,650 | 558,319
Public Service Company of New Mexico [Member] | Pension Plan [Member] | PNMR Master Trust [Member] | Estimate of Fair Value Measurement [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 78,461 |
Fair value of plan assets at end of year | 75,685 | 78,461
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 73,829 | 74,139
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 72,952 | 78,175
Fair value of plan assets at end of year | 72,694 | 72,952
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,512 |
Fair value of plan assets at end of year | 2,567 | 1,512
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 10,604 |
Fair value of plan assets at end of year | 9,300 | 10,604
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 9,367 |
Fair value of plan assets at end of year | 10,260 | 9,367
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 5,894 |
Fair value of plan assets at end of year | 6,338 | 5,894
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 28,419 |
Fair value of plan assets at end of year | 26,405 | 28,419
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 18,343 |
Fair value of plan assets at end of year | 18,959 | 18,343
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 111,441 |
Fair value of plan assets at end of year | 129,624 | 111,441
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 38,124 | 35,116
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,512 |
Fair value of plan assets at end of year | 2,567 | 1,512
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 9,367 |
Fair value of plan assets at end of year | 10,260 | 9,367
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 5,894 |
Fair value of plan assets at end of year | 6,338 | 5,894
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 18,343 |
Fair value of plan assets at end of year | 18,959 | 18,343
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 367,698 |
Fair value of plan assets at end of year | 337,989 | 367,698
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 35,705 | 39,023
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 10,604 |
Fair value of plan assets at end of year | 9,300 | 10,604
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 28,419 |
Fair value of plan assets at end of year | 26,405 | 28,419
Public Service Company of New Mexico [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year |  | 655
Actual return on assets sold during the period | 1 | 0
Actual return on assets still held at period end | 19 | (1)
Purchases | 0 | 177
Sales | (387) | (112)
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 719 |
Fair value of plan assets at end of year | 352 | 719
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Public Service Company of New Mexico [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Pension Plan [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 62,082 | 69,177
Fair value of plan assets at end of year | 60,624 | 62,082
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | PNMR Master Trust [Member] | Fair Value Measurement [Domain] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 52,163 |
Fair value of plan assets at end of year | 50,901 | 52,163
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 62,131 |
Fair value of plan assets at end of year | 60,630 | 62,131
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | PNMR Master Trust [Member] | Estimate of Fair Value Measurement [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 9,968 |
Fair value of plan assets at end of year | 9,729 | 9,968
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 8,778 | 9,290
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 9,111 | 10,094
Fair value of plan assets at end of year | 8,544 | 9,111
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 128 |
Fair value of plan assets at end of year | 308 | 128
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,310 |
Fair value of plan assets at end of year | 1,279 | 1,310
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 367 |
Fair value of plan assets at end of year | 449 | 367
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,013 |
Fair value of plan assets at end of year | 1,089 | 1,013
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 3,397 |
Fair value of plan assets at end of year | 3,060 | 3,397
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 3,075 |
Fair value of plan assets at end of year | 2,593 | 3,075
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 12,199 |
Fair value of plan assets at end of year | 14,447 | 12,199
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 4,439 | 4,583
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 128 |
Fair value of plan assets at end of year | 308 | 128
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 367 |
Fair value of plan assets at end of year | 449 | 367
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,013 |
Fair value of plan assets at end of year | 1,089 | 1,013
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 3,075 |
Fair value of plan assets at end of year | 2,593 | 3,075
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 39,886 |
Fair value of plan assets at end of year | 36,416 | 39,886
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 4,339 | 4,707
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 1,310 |
Fair value of plan assets at end of year | 1,279 | 1,310
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 3,397 |
Fair value of plan assets at end of year | 3,060 | 3,397
Texas-New Mexico Power Company [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year |  | 72
Actual return on assets sold during the period | 0 | 0
Actual return on assets still held at period end | 2 | 0
Purchases | 0 | 17
Sales | (42) | (11)
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pension Plan [Member] | PNMR Master Trust [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 78 |
Fair value of plan assets at end of year | 38 | 78
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Total fair value of plan assets owned | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
Texas-New Mexico Power Company [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other Postretirement Benefits [Member] | Fixed income securities, Mutual funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Fair Value Measurement [Domain] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 532,021 |
Fair value of plan assets at end of year | 518,866 | 532,021
PNMR [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 620,450 |
Fair value of plan assets at end of year | 604,280 | 620,450
PNMR [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 14,525 |
Fair value of plan assets at end of year | 20,503 | 14,525
PNMR [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 36,675 |
Fair value of plan assets at end of year | 38,401 | 36,675
PNMR [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 34,769 |
Fair value of plan assets at end of year | 36,036 | 34,769
PNMR [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 25,407 |
Fair value of plan assets at end of year | 18,484 | 25,407
PNMR [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 30,531 |
Fair value of plan assets at end of year | 27,532 | 30,531
PNMR [Member] | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 214,218 |
Fair value of plan assets at end of year | 205,419 | 214,218
PNMR [Member] | Fixed Income Securities, U.S. Government [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 98,138 |
Fair value of plan assets at end of year | 94,359 | 98,138
PNMR [Member] | Fixed Income Securities, Municipals [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 16,647 |
Fair value of plan assets at end of year | 13,970 | 16,647
PNMR [Member] | Fixed Income Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 61,111 |
Fair value of plan assets at end of year | 64,162 | 61,111
PNMR [Member] | Private equity funds [Member] | Estimate of Fair Value Measurement [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 32,333 |
Fair value of plan assets at end of year | 27,060 | 32,333
PNMR [Member] | Hedge funds [Member] | Estimate of Fair Value Measurement [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 40,731 |
Fair value of plan assets at end of year | 42,070 | 40,731
PNMR [Member] | Real estate funds [Member] | Estimate of Fair Value Measurement [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 15,365 |
Fair value of plan assets at end of year | 16,284 | 15,365
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 123,640 |
Fair value of plan assets at end of year | 144,071 | 123,640
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 14,525 |
Fair value of plan assets at end of year | 20,503 | 14,525
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 34,769 |
Fair value of plan assets at end of year | 36,036 | 34,769
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 25,407 |
Fair value of plan assets at end of year | 18,484 | 25,407
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Fixed Income Securities, U.S. Government [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 48,936 |
Fair value of plan assets at end of year | 69,048 | 48,936
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Fixed Income Securities, Municipals [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member} | Fixed Income Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 3 |
Fair value of plan assets at end of year | 0 | 3
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 407,584 |
Fair value of plan assets at end of year | 374,405 | 407,584
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 36,675 |
Fair value of plan assets at end of year | 38,401 | 36,675
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 30,531 |
Fair value of plan assets at end of year | 27,532 | 30,531
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 213,421 |
Fair value of plan assets at end of year | 205,029 | 213,421
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities, U.S. Government [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 49,202 |
Fair value of plan assets at end of year | 25,311 | 49,202
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities, Municipals [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 16,647 |
Fair value of plan assets at end of year | 13,970 | 16,647
PNMR [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fixed Income Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 61,108 |
Fair value of plan assets at end of year | 64,162 | 61,108
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 797 |
Fair value of plan assets at end of year | 390 | 797
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Cash and Cash Equivalents [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities, International Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities, Domestic Value [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities, Domestic Growth [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, Corporate [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 797 | 727
Actual return on assets sold during the period | 1 | 0
Actual return on assets still held at period end | 21 | (1)
Purchases | 0 | 194
Sales | (429) | (123)
Fair value of plan assets at end of year | 390 | 797
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, U.S. Government [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, Municipals [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Securities, Other Funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 0 |
Fair value of plan assets at end of year | 0 | 0
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Private equity funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 719 |
Fair value of plan assets at end of year | 352 | 719
PNMR [Member] | Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member] |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at beginning of year | 78 |
Fair value of plan assets at end of year | $ 38 | $ 78

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