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

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