Commitments and Contingencies - The Clean Air Act (Details)							1 Months Ended	12 Months Ended			35 Months Ended
	Feb. 09, 2016	Dec. 31, 2015 USD ($)	Dec. 16, 2015 USD ($) MWh MW	Oct. 23, 2015	Jul. 17, 2015	Dec. 20, 2013 USD ($) $ / kw MW	Aug. 31, 2011 generating_unit	Dec. 31, 2016 USD ($) lb / MMBTU generating_unit joint_owner MW	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jan. 31, 2016 USD ($)	Jan. 26, 2016 state	Jul. 31, 2015 MW	Aug. 06, 2012 compliance_alternative	Jul. 31, 2005 T	Dec. 31, 1999 state
Public Utilities, General Disclosures [Line Items]
Plant in service, held for future use, and to be abandoned		$ 6,307,261,000						$ 6,944,534,000	$ 6,307,261,000
Accumulated depreciation and amortization		2,058,772,000						2,334,938,000	2,058,772,000
Regulatory disallowances and restructuring costs								15,011,000	167,471,000	$ 1,062,000
Reversal of deferred items related to BART at SJGS								0	1,826,000	0
Four Corners [Member]
Public Utilities, General Disclosures [Line Items]
Approved lease extension term					25 years
Public Service Company of New Mexico [Member]
Public Utilities, General Disclosures [Line Items]
Plant in service, held for future use, and to be abandoned		4,833,303,000						5,359,211,000	4,833,303,000
Accumulated depreciation and amortization		1,569,549,000						1,809,528,000	1,569,549,000
Regulatory disallowances and restructuring costs								15,011,000	167,471,000	1,062,000
Reversal of deferred items related to BART at SJGS								$ 0	1,826,000	$ 0
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Number of units (in generating units) | generating_unit								4
Share of costs								46.30%
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member] | Surface [Member] | Loss on long-term purchase commitment [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory disallowances and restructuring costs		16,500,000							16,500,000
Estimate of possible loss								$ 102,000,000
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member]
Public Utilities, General Disclosures [Line Items]
Plant in service, held for future use, and to be abandoned		468,200,000						471,800,000	468,200,000
Accumulated depreciation and amortization		193,300,000						203,900,000	193,300,000
Construction work in progress		2,200,000							2,200,000
Net book value		$ 277,100,000						$ 267,900,000	277,100,000
Public Service Company of New Mexico [Member] | Four Corners [Member]
Public Utilities, General Disclosures [Line Items]
Number of units (in generating units) | generating_unit								2
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member]
Public Utilities, General Disclosures [Line Items]
Share of costs								13.00%
Plant in service, held for future use, and to be abandoned								$ 188,026,000
Accumulated depreciation and amortization								103,584,000
Construction work in progress								$ 52,869,000
PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Number of megawatts | MW								134
PNMR Development [Member] | Energy Equipment [Member]
Public Utilities, General Disclosures [Line Items]
Cost of installing equipment								$ 7,600,000
Environmental Protection Agency [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Number of units (in generating units) | generating_unit							4
Environmental Protection Agency and NMED [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Period of time to comply after approval							15 months
Clean Air Act related to Regional Haze [Member]
Public Utilities, General Disclosures [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 Air Act, SCR [Member] [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated total capital cost if requirement occurred								824,000,000
Clean Air Act, SCR [Member] [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated total capital cost if requirement occurred								$ 910,000,000
Clean Air Act, SNCR [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Number of other entities (in joint owner) | joint_owner								8
Clean Air Act, SNCR [Member] | San Juan Generating Station Unit 4 [Member] | CALIFORNIA
Public Utilities, General Disclosures [Line Items]
Number of other entities (in joint owner) | joint_owner								3
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member]
Public Utilities, General Disclosures [Line Items]
Estimated costs to remain unrecovered			$ 20,000,000
Regulatory disallowances and restructuring costs									$ 21,600,000
Net expense								$ 3,700,000
Reclamation expense								$ 4,500,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Overall reduction of ownership (in megawatts) | MW						340
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member]
Public Utilities, General Disclosures [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%	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
Accumulated plant write-off, disallowance								$ 128,600,000
Net carrying value								$ 139,300,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member] | Increase in coal mine decommissioning liability [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory disallowances and restructuring costs									165,700,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Estimated undepreciated value			$ 151,000,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Additional ownership to be obtained (in megawatts) | MW			65										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%
Ownership percentage								38.50%
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Percentage of ownership held by exiting owners								50.00%
Ownership percentage								50.00%
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Maximum [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Annual cost of renewable energy credits, maximum			$ 7,000,000.0
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Portion of costs for SNCRs and BDT equipment											$ 77,900,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Minimum [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated installation capital costs								$ 85,000,000
Estimated portion of total capital costs if requirement occurred								105,000,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Estimated installation capital costs								90,000,000
Estimated portion of total capital costs if requirement occurred								110,000,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Maximum [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Estimated installation capital costs						$ 82,000,000
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Scenario, Plan [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Ownership percentage													66.30%
Clean Air Act, SNCR [Member] | Public Service Company of New Mexico [Member] | Scenario, Plan [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Ownership percentage													77.30%
Clean Air Act, SNCR [Member] | PNMR and PNM [Member] | Palo Verde Nuclear Generating Station Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Number of megawatts | MW			134			134
Proposed value per kilowatt (in dollars per kilowatt) | $ / kw						2,500
Clean Air Act, SNCR [Member] | PNMR Development [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Additional ownership to be obtained (in megawatts) | MW													65
Reimbursement amount								$ 600,000
Potential acquisition of ownership (in megawatts) | MW													65
Restructuring fee									$ 3,100,000
Clean Air Act, SNCR Hearing Examiner Recommended Denial [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Additional ownership to be obtained (in megawatts) | MW			132
Clean Air Act, Post-2022 Coal Supply future rate case [Member] | Public Service Company of New Mexico [Member] | San Juan Generating Station Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Period of time for stipulation agreement			6 months
Clean Air Act Related to Post Combustion Controls [Member] | Public Service Company of New Mexico [Member] | Four Corners [Member]
Public Utilities, General Disclosures [Line Items]
Number of compliance alternatives | compliance_alternative														2
Government standard emissions limit (in pounds per MMBTU) | lb / MMBTU								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%
Estimate of possible loss								$ 90,400,000
Clean Air Act Related to Post Combustion Controls [Member] | Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member]
Public Utilities, General Disclosures [Line Items]
Ownership percentage								13.00%
Clean Power Plan [Member]
Public Utilities, General Disclosures [Line Items]
Period of potential extension to submit initial plans to meet environmental targets				2 years
Number of states that filed a petition against the Clean Power Plan | state												29
Proposed percentage reduction in CO2 emissions	32.00%
Period of time currently remaining to submit initial plans to meet environmental targets	6 months
Period of time currently remaining to submit initial plans to meet environmental targets, including potential extension	2 years 6 months