Financing - Activities, PNM and TNMP (Details)										1 Months Ended	12 Months Ended
	Feb. 01, 2017 USD ($)	Nov. 01, 2016 USD ($)	Feb. 01, 2016 USD ($)	Dec. 21, 2015 USD ($)	Aug. 11, 2015 USD ($)	May 08, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 27, 2014 USD ($)	Mar. 05, 2014 USD ($)	Jun. 21, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Feb. 21, 2017 USD ($)	Dec. 21, 2016 USD ($) loan	Oct. 21, 2016 USD ($)	Sep. 27, 2016 USD ($)	May 20, 2016 USD ($)	Dec. 17, 2015 USD ($)	Sep. 30, 2015	Jun. 01, 2015 USD ($)	Mar. 09, 2015 USD ($)	Dec. 22, 2014 USD ($)	Jan. 01, 2014 USD ($)	Dec. 09, 2013 USD ($)
Debt Instrument [Line Items]
Outstanding amount											$ 287,100,000	$ 250,600,000
Amount outstanding											100,000,000	50,000,000	$ 0
Fixed interest rate																				1.927%
Payment of debt											303,793,000	333,066,000	125,000,000
PNMR Term Loan Agreement [Member]
Debt Instrument [Line Items]
Outstanding amount											0	150,000,000
PNMR 2016 One-Year Term Loan and PNMR 2016 Two-Year Term Loan [Member]
Debt Instrument [Line Items]
Number of loan agreements (in loans) | loan															2
PNMR 2016 One Year Term Loan [Member]
Debt Instrument [Line Items]
Outstanding amount											$ 100,000,000				$ 100,000,000.0
Variable interest rate											1.60%
PNMR 2016 Two Year Term Loan [Member]
Debt Instrument [Line Items]
Loan entered into															100,000,000.0
Variable interest rate											1.69%
Level 2 [Member] | Cash Flow Hedging [Member]
Debt Instrument [Line Items]
Fair value gain (loss, less than)											$ (100,000)	100,000
Notes Payable to Banks [Member] | PNMR Term Loan Agreement [Member]
Debt Instrument [Line Items]
Outstanding amount																								$ 100,000,000.0
Amount outstanding				$ 150,000,000.0
Term Loan and Other Outstanding Debt [Member]
Debt Instrument [Line Items]
Repayments of debt									$ 75,000,000.0
NM Capital [Member] | San Juan Generating Station [Member] | Coal Supply [Member]
Debt Instrument [Line Items]
Payments to fund long-term loans to unaffiliated third party			$ 125,000,000
PNMR [Member] | PNMR 2016 Two Year Term Loan [Member]
Debt Instrument [Line Items]
Loan entered into											100,000,000	0
Public Service Company of New Mexico [Member]
Debt Instrument [Line Items]
Outstanding amount											61,000,000	0
Payment of debt											$ 271,000,000	214,300,000	75,000,000
Public Service Company of New Mexico [Member] | NMPRC [Member]
Debt Instrument [Line Items]
Requirement to obtain approval for any financing transaction, period of time (more than)											18 months
Texas-New Mexico Power Company [Member]
Debt Instrument [Line Items]
Outstanding amount											$ 0	59,000,000
Payment of debt											$ 0	0	$ 50,000,000
Repayments of debt								$ 30,000,000.0
Line of Credit [Member]
Debt Instrument [Line Items]
Debt-to-capital ratios (less than or equal to)											65.00%
Line of Credit [Member] | Texas-New Mexico Power Company [Member]
Debt Instrument [Line Items]
Debt-to-capital ratios (less than or equal to)											65.00%
PNMR 2015 Term Loan Agreement [Member]
Debt Instrument [Line Items]
Loan entered into															$ 150,000,000.0							$ 150,000,000.0
Variable interest rate											1.55%
Unsecured Debt [Member] | Senior unsecured notes, 9.25% due 2015 [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount																								$ 118,800,000
Stated percentage																								9.25%
Unsecured Debt [Member] | Public Service Company of New Mexico [Member]
Debt Instrument [Line Items]
Shelf registration statement, capacity of issuance (up to)											$ 250,000,000
Unsecured Debt [Member] | Public Service Company of New Mexico [Member] | 3.85% due 2025 [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount					$ 250,000,000.0						$ 250,000,000	250,000,000
Stated percentage					3.85%						3.85%
BTMU Term Loan Agreement [Member] | NM Capital [Member]
Debt Instrument [Line Items]
Loan entered into			$ 125,000,000.0								$ 92,200,000
Stated percentage											3.64%
Estimated principal payments											$ 42,000,000
BTMU Term Loan Agreement [Member] | NM Capital [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Loan entered into														$ 82,800,000
Payment of debt	$ 9,400,000
BTMU Term Loan Agreement [Member] | NM Capital [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt-to-capital ratio			65.00%
BTMU Term Loan Agreement [Member] | NM Capital [Member] | Minimum [Member]
Debt Instrument [Line Items]
Long-term debt, required quarterly payment		$ 5,000,000.0
Letter of Credit [Member] | PNMR [Member] | Letter or credit, 30 mil JP Morgan [Member]
Debt Instrument [Line Items]
Aggregate principal amount																$ 30,300,000
PNM 2014 Term Loan Agreement [Member] | Public Service Company of New Mexico [Member]
Debt Instrument [Line Items]
Loan entered into									$ 175,000,000.0
Repayments of debt					$ 175,000,000.0
PNM 2014 Multi-Draw Term Loan Agreement [Member] | Public Service Company of New Mexico [Member]
Debt Instrument [Line Items]
Loan entered into																							$ 125,000,000.0
Repayments of debt										$ 125,000,000.0
Outstanding borrowings						$ 25,000,000.0	$ 100,000,000.0
Unsecured notes, Pollution control revenue bonds [Member] | Public Service Company of New Mexico [Member] | Senior unsecured note, PCRB Due 2043, at 4 percent [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount																								$ 39,300,000
Unsecured notes, Pollution control revenue bonds [Member] | Public Service Company of New Mexico [Member] | Senior unsecured note, PCRB Due 2043, at 2 point 4 percent [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount																					$ 39,300,000
Stated percentage																					2.40%
PNM 2016 Term Loan Agreement [Member] | Public Service Company of New Mexico [Member]
Debt Instrument [Line Items]
Stated percentage											1.36%
Aggregate principal amount																		$ 175,000,000.0
Pollution Control Bonds [Member] | Public Service Company of New Mexico [Member] | Pollution Control Revenue Bonds 1 Point 875 Percent, due 2021 [Member]
Debt Instrument [Line Items]
Stated percentage																	1.875%
Aggregate principal amount																	$ 146,000,000
Pollution Control Bonds [Member] | Public Service Company of New Mexico [Member] | Pollution Control Revenue Bonds 1 Point 875 Percent, due 2021, 2016 Series A [Member]
Debt Instrument [Line Items]
Aggregate principal amount																	46,000,000
Pollution Control Bonds [Member] | Public Service Company of New Mexico [Member] | Pollution Control Revenue Bonds 1 Point 875 Percent, due 2021, 2016 Series B [Member]
Debt Instrument [Line Items]
Aggregate principal amount																	$ 100,000,000.0
Pollution Control Revenue Bonds [Member] | Texas-New Mexico Power Company [Member] | First Mortgage Bonds Due 2024, Series 2014A, at 4.03% [Member]
Debt Instrument [Line Items]
Stated percentage																									4.03%
Aggregate principal amount																									$ 80,000,000.0
2011 Term Loan Agreement [Member] | Texas-New Mexico Power Company [Member]
Debt Instrument [Line Items]
Repayments of debt								$ 50,000,000.0
First Mortgage Bonds [Member] | Texas-New Mexico Power Company [Member] | First Mortgage Bonds Due 2024, Series 2014A, at 4.03% [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount											$ 80,000,000	80,000,000
Stated percentage											4.03%
First Mortgage Bonds [Member] | Texas-New Mexico Power Company [Member] | First Mortgage Bonds 3 Point 53 Percent, due 2026, Series 2016A [Member]
Debt Instrument [Line Items]
Aggregate outstanding principal amount											$ 60,000,000	$ 0
Stated percentage											3.53%								3.53%
Aggregate principal amount																			$ 60,000,000.0