Fair Value of Derivative and Other Financial Instruments, Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
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	$ 587,909	$ 556,353
Fair value of plan assets at end of year	557,923	587,909
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	523,142
Fair value of plan assets at end of year	479,858	523,142
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	588,112
Fair value of plan assets at end of year	558,319	588,112
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	64,970
Fair value of plan assets at end of year	78,461	64,970
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	74,139	79,018
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	78,175	73,565
Fair value of plan assets at end of year	72,952	78,175
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	1,242
Fair value of plan assets at end of year	1,512	1,242
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	10,332
Fair value of plan assets at end of year	10,604	10,332
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	8,365
Fair value of plan assets at end of year	9,367	8,365
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	5,960
Fair value of plan assets at end of year	5,894	5,960
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	30,997
Fair value of plan assets at end of year	28,419	30,997
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	22,122
Fair value of plan assets at end of year	18,343	22,122
Public Service Company of New Mexico [Member] | 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	123,668
Fair value of plan assets at end of year	111,441	123,668
Public Service Company of New Mexico [Member] | Level 1 [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	35,116	37,689
Public Service Company of New Mexico [Member] | 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	1,242
Fair value of plan assets at end of year	1,512	1,242
Public Service Company of New Mexico [Member] | 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] | 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	8,365
Fair value of plan assets at end of year	9,367	8,365
Public Service Company of New Mexico [Member] | 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	5,960
Fair value of plan assets at end of year	5,894	5,960
Public Service Company of New Mexico [Member] | 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] | 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	22,122
Fair value of plan assets at end of year	18,343	22,122
Public Service Company of New Mexico [Member] | 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	398,819
Fair value of plan assets at end of year	367,698	398,819
Public Service Company of New Mexico [Member] | Level 2 [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	39,023	41,329
Public Service Company of New Mexico [Member] | 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] | 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	10,332
Fair value of plan assets at end of year	10,604	10,332
Public Service Company of New Mexico [Member] | 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] | 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] | 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	30,997
Fair value of plan assets at end of year	28,419	30,997
Public Service Company of New Mexico [Member] | 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] | 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		160
Actual return on assets sold during the period	0	0
Actual return on assets still held at period end	(1)	(18)
Purchases	177	546
Sales	(112)	(33)
Public Service Company of New Mexico [Member] | 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	655
Fair value of plan assets at end of year	719	655
Public Service Company of New Mexico [Member] | 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] | 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] | 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] | 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] | 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] | 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] | 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	69,177	66,118
Fair value of plan assets at end of year	62,082	69,177
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	59,320
Fair value of plan assets at end of year	52,163	59,320
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	69,207
Fair value of plan assets at end of year	62,131	69,207
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	9,887
Fair value of plan assets at end of year	9,968	9,887
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	9,290	10,211
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	10,094	9,601
Fair value of plan assets at end of year	9,111	10,094
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	168
Fair value of plan assets at end of year	128	168
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	1,277
Fair value of plan assets at end of year	1,310	1,277
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	403
Fair value of plan assets at end of year	367	403
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	1,024
Fair value of plan assets at end of year	1,013	1,024
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	3,790
Fair value of plan assets at end of year	3,397	3,790
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	3,549
Fair value of plan assets at end of year	3,075	3,549
Texas-New Mexico Power Company [Member] | 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	14,823
Fair value of plan assets at end of year	12,199	14,823
Texas-New Mexico Power Company [Member] | Level 1 [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	4,583	5,144
Texas-New Mexico Power Company [Member] | 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	168
Fair value of plan assets at end of year	128	168
Texas-New Mexico Power Company [Member] | 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] | 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	403
Fair value of plan assets at end of year	367	403
Texas-New Mexico Power Company [Member] | 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	1,024
Fair value of plan assets at end of year	1,013	1,024
Texas-New Mexico Power Company [Member] | 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] | 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	3,549
Fair value of plan assets at end of year	3,075	3,549
Texas-New Mexico Power Company [Member] | 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	44,425
Fair value of plan assets at end of year	39,886	44,425
Texas-New Mexico Power Company [Member] | Level 2 [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets owned	4,707	5,067
Texas-New Mexico Power Company [Member] | 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] | 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	1,277
Fair value of plan assets at end of year	1,310	1,277
Texas-New Mexico Power Company [Member] | 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] | 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] | 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	3,790
Fair value of plan assets at end of year	3,397	3,790
Texas-New Mexico Power Company [Member] | 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] | 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		16
Actual return on assets sold during the period	0	0
Actual return on assets still held at period end	0	(2)
Purchases	17	62
Sales	(11)	(4)
Texas-New Mexico Power Company [Member] | 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	72
Fair value of plan assets at end of year	78	72
Texas-New Mexico Power Company [Member] | 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] | 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] | 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] | 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] | 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] | 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] | 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	582,462
Fair value of plan assets at end of year	532,021	582,462
PNMR [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	657,319
Fair value of plan assets at end of year	620,450	657,319
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	15,645
Fair value of plan assets at end of year	14,525	15,645
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	23,282
Fair value of plan assets at end of year	36,675	23,282
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	41,778
Fair value of plan assets at end of year	34,769	41,778
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	28,370
Fair value of plan assets at end of year	25,407	28,370
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	29,719
Fair value of plan assets at end of year	30,531	29,719
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	242,742
Fair value of plan assets at end of year	214,218	242,742
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	106,634
Fair value of plan assets at end of year	98,138	106,634
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	20,156
Fair value of plan assets at end of year	16,647	20,156
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	74,136
Fair value of plan assets at end of year	61,111	74,136
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	37,220
Fair value of plan assets at end of year	32,333	37,220
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	23,876
Fair value of plan assets at end of year	40,731	23,876
PNMR [Member] | Real Estate [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	13,761
Fair value of plan assets at end of year	15,365	13,761
PNMR [Member] | Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	138,491
Fair value of plan assets at end of year	123,640	138,491
PNMR [Member] | 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	15,645
Fair value of plan assets at end of year	14,525	15,645
PNMR [Member] | 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] | 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	41,778
Fair value of plan assets at end of year	34,769	41,778
PNMR [Member] | 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	28,370
Fair value of plan assets at end of year	25,407	28,370
PNMR [Member] | 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] | 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] | 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	52,537
Fair value of plan assets at end of year	48,936	52,537
PNMR [Member] | 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] | 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	161
Fair value of plan assets at end of year	3	161
PNMR [Member] | Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	443,244
Fair value of plan assets at end of year	407,584	443,244
PNMR [Member] | 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] | 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	23,282
Fair value of plan assets at end of year	36,675	23,282
PNMR [Member] | 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] | 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] | 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	29,719
Fair value of plan assets at end of year	30,531	29,719
PNMR [Member] | 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	242,015
Fair value of plan assets at end of year	213,421	242,015
PNMR [Member] | 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	54,097
Fair value of plan assets at end of year	49,202	54,097
PNMR [Member] | 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	20,156
Fair value of plan assets at end of year	16,647	20,156
PNMR [Member] | 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	73,975
Fair value of plan assets at end of year	61,108	73,975
PNMR [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	727
Fair value of plan assets at end of year	797	727
PNMR [Member] | 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] | 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] | 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] | 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] | 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] | 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	727	176
Actual return on assets sold during the period	0	0
Actual return on assets still held at period end	(1)	(20)
Purchases	194	608
Sales	(123)	(37)
Fair value of plan assets at end of year	797	727
PNMR [Member] | 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] | 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] | 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] | 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	655
Fair value of plan assets at end of year	719	655
PNMR [Member] | 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	72
Fair value of plan assets at end of year	$ 78	$ 72