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