Commitments and Contingencies (Details)											1 Months Ended	3 Months Ended		12 Months Ended			35 Months Ended
	Feb. 01, 2016 USD ($)	Dec. 31, 2015 USD ($) MW	Dec. 21, 2015	Oct. 29, 2015 USD ($)	Aug. 17, 2015 USD ($)	Aug. 13, 2015 USD ($) MWh MW	Jul. 17, 2015	Mar. 02, 2015 lb / MMBTU T	May. 16, 2014 USD ($)	Dec. 20, 2013 USD ($) $ / kw MW	May. 31, 2010 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) MW	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jan. 31, 2016 USD ($)	Feb. 09, 2016	Jan. 26, 2016 state	Dec. 02, 2015 Allotment_Parcel	Oct. 01, 2015 opp	Sep. 30, 2015 opp	Aug. 11, 2015 T	Jul. 31, 2015 MW	Jul. 13, 2015 a	May. 19, 2015 MW	May. 14, 2015 lb / MMBTU	Jan. 22, 2015 Allotment_Parcel	Jan. 07, 2015 MW	Jun. 30, 2014 USD ($) MW	May. 31, 2014 USD ($)	Apr. 02, 2014 Allotment_Parcel	Jan. 06, 2014 Allotment_Parcel	Dec. 30, 2013 lb / Decatherm	Aug. 31, 2013	May. 23, 2013 USD ($)	Oct. 31, 2012 USD ($)	Sep. 30, 2012 landowner	Aug. 06, 2012 compliance_alternative	Dec. 31, 2011 mw	Jan. 31, 2010 opp	Aug. 31, 2006 USD ($)	Jul. 31, 2005 T	Dec. 31, 2003	Dec. 31, 1999 state
Loss Contingencies [Line Items]
Plant in Service		$ 6,307,261,000												$ 6,307,261,000	$ 5,941,581,000
Accumulated Depreciation		(2,058,772,000)												(2,058,772,000)	(1,939,760,000)
Regulatory disallowances and restructuring costs														167,471,000	1,062,000	$ 12,235,000
Reversal of deferred items related to BART at SJGS														1,826,000	0	0
Other current assets		82,104,000												82,104,000	58,471,000
San Juan Generating Station [Member] | Continuous Highwall Mining [Member]
Loss Contingencies [Line Items]
Proposed retroactive surface mining royalty rate																																			12.50%
Surface mining royalty rate applied between 2000 and 2003																																												8.00%
Estimated underpaid surface mining royalties under proposed rate change																																										$ 5,000,000
PNM's share of estimated underpaid surface mining royalties under proposed rate change																																										46.30%
San Juan Generating Station [Member] | SJCC Arbitration [Member]
Loss Contingencies [Line Items]
Potential unbilled mining costs owed to SJCC																															$ 5,200,000
Potential overbilled mining costs SJCC owes to SJGS owners																															1,100,000
Potential capital improvements billed as mining costs to SJGS owners																															$ 13,900,000
Clean Air Act related to Regional Haze [Member]
Loss Contingencies [Line Items]
Number of states to address regional haze | state																																													50
Potential to emit tons per year of visibility impairing pollution, maximum (in tons) | T																																											250
Clean Power Plan [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
Number of states that filed a petition against the Clean Power Plan | state																			29
Proposed percentage reduction in CO2 emissions																		32.00%
San Juan Generating Station Unit 4 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Unsubscribed ownership (in megawatts) | MW																													65
Four Corners [Member]
Loss Contingencies [Line Items]
Third party sale of ownership percentage																																		48.00%
Approved lease extension term							25 years
Period of time to remedy violations until suit is filed			60 days
Four Corners [Member] | NMTRD Coal Severance Tax [Member]
Loss Contingencies [Line Items]
Assessed coal severance surtax penalty and interest																																				$ 30,000,000
Public Service Company of New Mexico [Member]
Loss Contingencies [Line Items]
Plant in Service		4,833,303,000												4,833,303,000	4,581,066,000
Accumulated Depreciation		(1,569,549,000)												(1,569,549,000)	(1,486,406,000)
Regulatory disallowances and restructuring costs														167,471,000	1,062,000	12,235,000
Reversal of deferred items related to BART at SJGS														1,826,000	0	0
Other current assets		74,990,000												74,990,000	53,095,000
Regulatory assets		342,910,000												342,910,000	401,025,000
Public Service Company of New Mexico [Member] | SPS Complaint, Federal Power Act [Member]
Loss Contingencies [Line Items]
Proposed settlement pending regulatory approval				$ 4,200,000
Portion of proposed settlement to be credited to customers, pending regulatory approval				$ 2,600,000
Public Service Company of New Mexico [Member] | Navajo Nation Allottee Matters [Member]
Loss Contingencies [Line Items]
Number of landowners claiming to be Navajo allottees (in landowners) | landowner																																						43
Number of allotment parcels' appraisal requested for review (in allotment parcels) | Allotment_Parcel																																	58
Number of allotments where landowners are revoking rights of way renewal consents | Allotment_Parcel																																6
Number of allotments, Previously contested rights of way renewal consents | Allotment_Parcel																												10
Acres of land at issue (in acres) | a																									15.49
Number of allotment parcels' at issue, Not to be condemned | Allotment_Parcel																				2
Number of allotment parcels' at issue | Allotment_Parcel																				5
Public Service Company of New Mexico [Member] | Surface [Member]
Loss Contingencies [Line Items]
Regulatory assets		100,000,000												100,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | SJCC Arbitration [Member]
Loss Contingencies [Line Items]
PNM's share of arbitration ruling																															46.30%
FFPAC percentage of mining costs overbilled or unbilled ruled by arbitration																															33.00%
Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Estimated costs to remain unrecovered						$ 20,000,000
Regulatory disallowances and restructuring costs														21,600,000
Public Service Company of New Mexico [Member] | National Ambient Air Quality Standards, 2015 EPA Legal Settlement [Member]
Loss Contingencies [Line Items]
Period of time to act on settlement								16 months
Emissions tons of SO2 per year | T								16,000
Public Service Company of New Mexico [Member] | National Ambient Air Quality Standards, 2015 EPA Legal Settlement [Member] | Minimum [Member]
Loss Contingencies [Line Items]
SO2 emissions rate (in pounds per MMBTU) | lb / MMBTU								0.45
Emissions tons of SO2 per year | T								2,600															2,000
Public Service Company of New Mexico [Member] | National Ambient Air Quality Standards [Member] | San Juan Generating Station [Member]
Loss Contingencies [Line Items]
Revised SO2 emissions agreed upon (in pounds per MMBTU) | lb / MMBTU																											0.10
Public Service Company of New Mexico [Member] | Loss on long-term purchase commitment [Member] | San Juan Generating Station [Member]
Loss Contingencies [Line Items]
Annual funding post-term reclamation trust														4,300,000	1,000,000	300,000
Public Service Company of New Mexico [Member] | Mine Reclamation Trust [Member] | San Juan Generating Station [Member]
Loss Contingencies [Line Items]
Reclamation trust funding, next fiscal year		4,900,000												4,900,000
Reclamation trust funding, year 2		5,400,000												5,400,000
Public Service Company of New Mexico [Member] | Mine Reclamation Trust [Member] | Four Corners [Member]
Loss Contingencies [Line Items]
Reclamation trust funding, next fiscal year		1,900,000												1,900,000
Reclamation trust funding, year 2		2,000,000												2,000,000
Reclamation trust funding, year 3		2,100,000												2,100,000
Public Service Company of New Mexico [Member] | Loss on long-term purchase commitment [Member] | Surface [Member]
Loss Contingencies [Line Items]
Liability for interim storage costs		38,800,000												38,800,000	25,700,000
Final reclamation, capped amount to be collected														100,000,000.0
Public Service Company of New Mexico [Member] | Loss on long-term purchase commitment [Member] | Underground [Member]
Loss Contingencies [Line Items]
Liability for interim storage costs		11,400,000												11,400,000	8,600,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member]
Loss Contingencies [Line Items]
Funding for decommissioning costs in qualified and non-qualified trust funds														4,900,000	4,900,000	$ 4,900,000
Estimated market value of trusts for decommissioning costs		$ 249,100,000												$ 249,100,000	244,600,000
Composite Interest		10.20%												10.20%
Plant in Service		$ 562,412,000												$ 562,412,000
Accumulated Depreciation		(164,549,000)												(164,549,000)
Construction Work in Progress		$ 38,966,000												$ 38,966,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Nuclear Plant [Member]
Loss Contingencies [Line Items]
Ownership percentage in nuclear reactor		10.20%												10.20%
Maximum potential assessment per incident		$ 38,900,000												$ 38,900,000
Annual payment limitation related to incident		5,800,000												5,800,000
Aggregate amount of all risk insurance		2,750,000,000.00												2,750,000,000.00
Sublimit amount under nuclear electric insurance limited		2,250,000,000.00												2,250,000,000.00
Maximum amount under nuclear electric insurance limited		5,400,000												5,400,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Nuclear Plant [Member] | Commercial Providers [Member]
Loss Contingencies [Line Items]
Liability insurance coverage		375,000,000												375,000,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Nuclear Plant [Member] | Industry Wide Retrospective Assessment Program [Member]
Loss Contingencies [Line Items]
Liability insurance coverage		13,100,000,000.0												13,100,000,000.0
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Maximum [Member] | Nuclear Plant [Member]
Loss Contingencies [Line Items]
Liability insurance coverage		13,500,000,000												13,500,000,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Department of energy, spent nuclear fuel removal January 2007 - June 2011 [Member]
Loss Contingencies [Line Items]
PNM's share of third party settlement claim															5,900,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Department of energy, spent nuclear fuel removal July 2011 - June 2014 [Member]
Loss Contingencies [Line Items]
PNM's share of third party settlement claim													$ 4,300,000
Litigation settlement, portion credited to customers													$ 3,100,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Department of energy, spent nuclear fuel removal July 2014 - June 2015 [Member]
Loss Contingencies [Line Items]
PNM's share of third party settlement claim												$ 1,300,000
Litigation settlement, portion credited to customers												$ 500,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Nuclear spent fuel and waste disposal [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		58,000,000												58,000,000
Annual fee, nuclear waste disposal									$ 0
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station [Member] | Nuclear spent fuel and waste disposal [Member] | Other Deferred Credits [Member]
Loss Contingencies [Line Items]
Liability for interim storage costs		$ 12,200,000												$ 12,200,000	12,300,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Loss Contingencies [Line Items]
Composite Interest																																					46.30%
Minimum megawatt capacity from coal and oil-fired electric generating units under jurisdiction of the Mercury and Air Toxics Standards (in megawatts) | mw																																								25
Mercury removal efficiency		99.00%												99.00%
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Coal Supply [Member]
Loss Contingencies [Line Items]
Other current assets		$ 49,000,000												$ 49,000,000	$ 37,300,000
Estimated increase in coal cost		40.00%												40.00%
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Clean Air Act, SCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Estimated total capital cost if requirement occurred																																					$ 824,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Clean Air Act, SCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Estimated total capital cost if requirement occurred																																					910,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Overall reduction of ownership (in megawatts) | MW										340
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Clean Air Act, SNCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Estimated installation capital costs																																					85,000,000
Estimated portion of total capital costs if requirement occurred																																					105,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Clean Air Act, SNCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Estimated installation capital costs																																					90,000,000
Estimated portion of total capital costs if requirement occurred																																					$ 110,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Mercury Control [Member]
Loss Contingencies [Line Items]
Current annual mercury control costs											$ 700,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Mercury Control [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Contingent estimated annual mercury control cost											$ 6,600,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Loss on long-term purchase commitment [Member] | Surface [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		$ 98,200,000												$ 98,200,000
Regulatory disallowances and restructuring costs		16,500,000												16,500,000
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Loss on long-term purchase commitment [Member] | Underground [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		118,900,000												118,900,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member]
Loss Contingencies [Line Items]
Plant in Service		468,200,000												468,200,000
Accumulated Depreciation		(193,300,000)												(193,300,000)
Construction Work in Progress		2,200,000												2,200,000
Net book value		$ 277,100,000												$ 277,100,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Requested time period to recover retired units NBV						20 years				20 years				20 years
Number of megawatts of gas-fired generation (in megawatts) | MW										177
Newly identified replacement solar generation (in megawatts) | MW										40
Current ownership (in megawatts) | MW						418
Recovery percentage of estimated undepreciated value		50.00%				50.00%								50.00%
Estimated undepreciated value		$ 255,300,000												$ 255,300,000
Regulatory disallowances and restructuring costs														127,600,000
Reversal of deferred items related to BART at SJGS														1,800,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] | Increase in coal mine decommissioning liability [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Regulatory disallowances and restructuring costs														$ 165,700,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Estimated undepreciated value						$ 150,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 1 and 4 [Member]
Loss Contingencies [Line Items]
Proposed proportionate ownership share																														58.70%
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 1 and 4 [Member] | Clean Air Act, SNCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
Total costs for SNCRs and BDT equipment																	$ 78,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 1 and 4 [Member] | Clean Air Act, SNCR [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Estimated installation capital costs										$ 82,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member]
Loss Contingencies [Line Items]
Proposed proportionate ownership share																														64.50%
Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Additional ownership to be obtained (in megawatts) | MW						65																		132		132				132
Estimated rate base value						$ 0
Coal-fired generation (in megawatts) | MW						197
Number of megawatt hours of renewable energy certificates to be acquired and retired (in megawatt hours) | MWh						1
Percentage of ownership held by exiting owners		38.80%												38.80%
Ownership percentage		38.50%												38.50%
Costs to obtain additional ownership																														$ 0
Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] | Clean Air Act, SNCR [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Annual cost of renewable energy credits, maximum						$ 7,000,000.0
Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member] | Clean Air Act, SNCR Hearing Examiner Recommended Denial [Member]
Loss Contingencies [Line Items]
Additional ownership to be obtained (in megawatts) | MW						132
Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 3 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Percentage of ownership held by exiting owners		50.00%												50.00%
Ownership percentage		50.00%												50.00%
Public Service Company of New Mexico [Member] | Four Corners [Member] | Clean Air Act related to Post-Combustion Controls [Member]
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		$ 94,000,000												$ 94,000,000
Number of compliance alternatives | compliance_alternative																																							2
Government standard emissions limit (pounds per MMBTU, parts per million) | lb / Decatherm																																		0.015
Plant requirement to meet opacity limit																																		20.00%
Rule imposes opacity limitation on certain fugitive dust emissions from coal and material handling operations																																		20.00%
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member]
Loss Contingencies [Line Items]
Composite Interest		13.00%												13.00%
Plant in Service		$ 167,874,000												$ 167,874,000
Accumulated Depreciation		(102,559,000)												(102,559,000)
Construction Work in Progress		$ 19,390,000												$ 19,390,000
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member] | Clean Air Act related to Post-Combustion Controls [Member]
Loss Contingencies [Line Items]
Ownership percentage																																		13.00%
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member] | Clean Air Act Lawsuit [Member]
Loss Contingencies [Line Items]
Ownership percentage					13.00%
Litigation settlement, amount					$ 1,500,000
Litigation settlement, expected capital spend, environmental					$ 6,700,000
Public Service Company of New Mexico [Member] | San Juan Generating Station And Four Corners [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Proposed government standard emission limit (in ozone parts per million) | opp																																									60
Public Service Company of New Mexico [Member] | San Juan Generating Station And Four Corners [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Government standard emissions limit (pounds per MMBTU, parts per million) | opp																					70	75
Proposed government standard emission limit (in ozone parts per million) | opp																																									70
PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member]
Loss Contingencies [Line Items]
Number of megawatts not included in retail rates (in megawatts) | MW		134												134
PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Number of megawatts not included in retail rates (in megawatts) | MW						134				134
Proposed value per kilowatt (in dollars per kilowatt) | $ / kw										2,500
NM Capital [Member] | Subsequent Event [Member] | BTMU Term Loan Agreement [Member]
Loss Contingencies [Line Items]
Long-term debt	$ 125,000,000.0
NM Capital [Member] | San Juan Generating Station [Member] | Subsequent Event [Member] | Coal Supply [Member]
Loss Contingencies [Line Items]
Payments to fund long-tern loans to unaffiliated third party	125,000,000.0
Loan agreement	$ 125,000,000.0
Variable interest rate	7.25%
Coal mine reclamation bonds to be posted with NMMMD	$ 161,600,000
Cash used to support bank letter or credit arrangement	$ 40,000,000
Number of days to provide security interest	180 days
PNMR Development [Member] | San Juan Generating Station Unit 4 [Member] | Clean Air Act, SNCR [Member]
Loss Contingencies [Line Items]
Potential acquisition of ownership (in megawatts) | MW																								65		65
Other income, restructuring fee														$ 3,100,000