Regulatory and Rate Matters - PNM (Details)								3 Months Ended		6 Months Ended		12 Months Ended	40 Months Ended
	Aug. 05, 2016	Aug. 04, 2016 USD ($)	Apr. 15, 2016 USD ($) GWh	Jan. 21, 2016 MW	Jan. 15, 2016 LeaseAgreements	Aug. 27, 2015 USD ($)	Mar. 20, 2015 USD ($) party	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($) MW	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($) MW	Dec. 31, 2015	Jun. 30, 2016 USD ($)	Jul. 08, 2016 MW	Apr. 26, 2016 USD ($) turbine MW	Feb. 26, 2016 USD ($)	Jan. 31, 2016 MW	Dec. 31, 2013	Mar. 01, 2013	Dec. 31, 2012 USD ($)
Public Service Company of New Mexico [Member] | San Juan Generating Station Units 2 and 3 [Member]
Public Utilities, General Disclosures [Line Items]
Net book value								$ 272,200,000		$ 272,200,000			$ 272,200,000
Public Service Company of New Mexico [Member] | Clean Air Act, Balanced Draft Technology [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Net book value								51,300,000		51,300,000			51,300,000
Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member] | San Juan Generating Station Units 2 and 3 [Member]
Public Utilities, General Disclosures [Line Items]
Newly identified replacement gas-fired generation (in megawatts) | MW									187		187				80
Number of aeroderivative units (in turbines) | turbine															2
Replacement gas-fired aeroderivative generation (in megawatts) | MW															40
Cost of replacement gas-fired unit															$ 86,800,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases [Member]
Public Utilities, General Disclosures [Line Items]
Number of megawatts purchased (in megawatts) | MW																	64.1
Number of leases under which assets were purchased | LeaseAgreements					3
Estimated annual property tax expense								800,000		800,000			800,000
Number of leases under which lease term was extended | LeaseAgreements					1
Lease term extension period					8 years
Net book value								161,300,000		161,300,000			161,300,000
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 1 Leases, extended [Member]
Public Utilities, General Disclosures [Line Items]
Estimated annual property tax expense								1,500,000		1,500,000			1,500,000
Estimated annual rent expense								18,100,000		18,100,000			18,100,000
Number of leases under which lease term was extended | LeaseAgreements					4
Lease term extension period					8 years
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Units 1 and 2 Leases [Member]
Public Utilities, General Disclosures [Line Items]
Estimated annual property tax expense								2,300,000		2,300,000			2,300,000
Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Clean Air Act, Balanced Draft Technology [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Installation costs													52,300,000
Public Service Company of New Mexico [Member] | Installation Costs Including Construction Management, Gross Receipts Taxes, AFUDC, and Other PNM Costs [Member] | Clean Air Act, SNCR [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Installation costs													76,800,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested rate increase (decrease)						$ 123,500,000
Requested rate increase (decrease) of non-fuel revenue						$ 121,700,000				121,500,000
Requested return on equity						10.50%
Requested rate increase (decrease) for fuel related costs										(42,900,000)
Requested rate increase (decrease) for non-fuel related revenues										(200,000)
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Clean Air Act, Balanced Draft Technology [Member] | San Juan Generating Station Units 1 and 4 [Member]
Public Utilities, General Disclosures [Line Items]
Requested base rate increase (decrease)						$ 40,000,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's recommended rate increase (decrease) of non-fuel revenue		$ 41,300,000
Hearing examiner's recommended return on equity		9.575%
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's proposed disallowance of recovery		$ 163,300,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Palo Verde Nuclear Generating Station, Unit 1 Leases, extended [Member]
Public Utilities, General Disclosures [Line Items]
Future minimum payments due								120,300,000		120,300,000			120,300,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Palo Verde Nuclear Generating Station, Unit 1 Leases, extended [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's recommended rent expense recovery amount		0
Hearing examiner's recommended recovery amount on conversions		0
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Palo Verde Nuclear Generating Station, Units 1 and 2 Leases [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's recommended property tax recovery amount		0
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Alvarado square [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory assets								$ 4,000,000		$ 4,000,000			$ 4,000,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Alvarado square [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's recommended amount to not be recovered from retail customers		$ 4,000,000
Public Service Company of New Mexico [Member] | 2015 Electric Rate Case [Member] | Refined Coal [Member] | Subsequent Event [Member] | San Juan Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Hearing examiner's recommended percentage of revenue to be credited to customers		100.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Reasonable cost threshold								3.00%		3.00%			3.00%					3.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Wind Energy [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of diversification								30.00%		30.00%			30.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Solar Energy [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of diversification								20.00%		20.00%			20.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Distributed Generation [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of diversification								3.00%		3.00%			3.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Renewable Technologies [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of diversification								5.00%		5.00%			5.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2011 [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of renewable energy in portfolio to electric sales								10.00%		10.00%			10.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of renewable energy in portfolio to electric sales								15.00%		15.00%			15.00%
Public Service Company of New Mexico [Member] | Renewable Portfolio Standard [Member] | Required Percentage by 2020 [Member]
Public Utilities, General Disclosures [Line Items]
Required percentage of renewable energy in portfolio to electric sales								20.00%		20.00%			20.00%
Public Service Company of New Mexico [Member] | Renewable Energy Rider [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Approved return on equity										10.50%		10.50%
Proposal to collect funds under renewable energy procurement plan								$ 42,400,000		$ 42,400,000			$ 42,400,000
Annual revenue to be collected under rider rate								50,000,000		$ 50,000,000			$ 50,000,000
Public Service Company of New Mexico [Member] | 2017 Energy Efficiency and Load Management Program [Member] | Disincentives / Incentives Adder [Member]
Public Utilities, General Disclosures [Line Items]
Program portfolio's total budget			$ 28,000,000
Incentive based on target savings			$ 2,400,000
Targeted savings (in gigawatt hours) | GWh			75
Public Service Company of New Mexico [Member] | Integrated Resource Plan, 2011 [Member]
Public Utilities, General Disclosures [Line Items]
Frequency of IRP filings										3 years
Planning period covered of IRP										20 years
Public Service Company of New Mexico [Member] | Advanced Metering Infrastructure Costs [Member]
Public Utilities, General Disclosures [Line Items]
Estimated costs to be recovered																$ 87,200,000
Estimated future investment																$ 33,000,000
Public Service Company of New Mexico [Member] | Advanced Metering Infrastructure Costs [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Period of time to either request a new hearing or withdraw application with regulatory body	60 days
Public Service Company of New Mexico [Member] | Formula Transmission Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Amount of regulatory costs not yet approved																				$ 3,200,000
Return on equity							10.00%													10.81%
Percentage ownership of EIP transmission line																			60.00%
Number of other parties entered into settlement agreement | party							5
Approved rate increase (decrease)							$ 1,300,000
Public Service Company of New Mexico [Member] | Firm Requirements Wholesale Power Rate Case, Navopache [Member] [Member]
Public Utilities, General Disclosures [Line Items]
Number of megawatts served under a short-term coordination tariff | MW				10
Revenue for power sold under PSA								$ 4,700,000	$ 6,400,000	$ 10,000,000	$ 13,400,000
PNMR Development [Member] | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW														30