Financing - Financing Activities (Details)													3 Months Ended	12 Months Ended
	Nov. 15, 2023 USD ($)	Jun. 30, 2023 USD ($)	May 15, 2023 USD ($)	Nov. 10, 2022 USD ($) $ / shares	Sep. 30, 2022 USD ($)	Aug. 05, 2022 USD ($)	Jan. 24, 2022 USD ($)	Dec. 02, 2021 USD ($)	Jul. 14, 2021 USD ($)	Jun. 18, 2021 USD ($)	May 18, 2021 USD ($)	Mar. 09, 2021 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Jun. 01, 2023 USD ($)	Apr. 28, 2023 USD ($) bond debtInstrument	Jun. 01, 2022 USD ($) derivative	Apr. 27, 2022 USD ($) bond	Oct. 01, 2021 USD ($)	Aug. 16, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 22, 2020 USD ($)	Dec. 21, 2020 USD ($)
Debt Instrument [Line Items]
Common stock, no par value (in dollars per share) | $ / shares														$ 0	$ 0
Repayments of debt														$ 910,000,000	$ 179,500,000	$ 1,411,345,000
Current maturities of long-term debt														280,169,000	184,793,000
Other Current Assets
Debt Instrument [Line Items]
Cash flow hedge derivative instrument assets at fair value														7,200,000	11,100,000
Other Deferred Costs Net Including Deferred Finance Costs
Debt Instrument [Line Items]
Cash flow hedge derivative instrument assets at fair value														2,300,000
Cash Flow Hedge | Interest rate contract
Debt Instrument [Line Items]
Derivative asset, number of instruments held | derivative																			2
PNMR 2022 ATM Program
Debt Instrument [Line Items]
Distribution agreement, sale of stock				$ 200,000,000
Common stock, no par value (in dollars per share) | $ / shares				$ 0
PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Term loans																								$ 300,000,000
PNMR 2019 Term Loan
Debt Instrument [Line Items]
Term loans																									$ 150,000,000
PNMR 2020 Term Loan
Debt Instrument [Line Items]
Term loans																									$ 150,000,000
PNM 2021 Note Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount									$ 160,000,000
PNMR 2021 Delayed-Draw Term Loan due May 2025
Debt Instrument [Line Items]
Repayments of debt		$ 500,000,000
Securitized Bonds
Debt Instrument [Line Items]
Current maturities of long-term debt														2,529,000	0
Maximum | Related Party
Debt Instrument [Line Items]
Notes payable														150,000,000
PNMR | Related Party
Debt Instrument [Line Items]
Notes payable														0	5,300,000
PNMR | PNMR 2018 SUNs
Debt Instrument [Line Items]
Repayments of debt												$ 80,000,000
PNMR | PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Financing capacity												$ 220,000,000
PNMR | PNMR 2021 Delayed-Draw Term Loan due May 2025
Debt Instrument [Line Items]
Term loans														$ 500,000,000	$ 1,000,000,000
PNM
Debt Instrument [Line Items]
Maturity term over which financings require regulator approval (more than)														18 months
Common stock, no par value (in dollars per share) | $ / shares														$ 0	$ 0
Repayments of debt														$ 410,000,000	$ 179,500,000	446,345,000
Current maturities of long-term debt														200,222,000	184,793,000
PNM | 5.51% due April 2035
Debt Instrument [Line Items]
Aggregate principal amount																							$ 40,000,000
Repayments of debt										$ 40,000,000
PNM | Securitized Bonds
Debt Instrument [Line Items]
Current maturities of long-term debt														2,529,000	0
TNMP
Debt Instrument [Line Items]
Current maturities of long-term debt														79,947,000	0
PNM and TNMP | Related Party
Debt Instrument [Line Items]
Notes payable														0	0
PNMR Development | Related Party
Debt Instrument [Line Items]
Notes payable														$ 2,300,000	0
Line of Credit | PNMR 2021 Delayed-Draw Term Loan due May 2025 | Revolving Credit Facility
Debt Instrument [Line Items]
Proceeds from long-term lines of credit							$ 100,000,000	$ 50,000,000			$ 850,000,000
Interest rates on outstanding borrowings														6.43%
Line of Credit | PNMR Development Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of debt											40,000,000
Line of Credit | PNMR Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Repayments of debt											92,100,000
Line of Credit | PNM 2022 Delayed-Draw Term Loan | Revolving Credit Facility
Debt Instrument [Line Items]
Financing capacity						$ 225,000,000
Repayments of debt	$ 225,000,000
Proceeds from long-term lines of credit					$ 45,000,000	$ 180,000,000
Line of Credit | PNMR and PNMR Development
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)														70.00%
Line of Credit | PNM and TNMP
Debt Instrument [Line Items]
Ratio of debt to capital (less than or equal to)														65.00%
Bonds | PNMR 2020 Delayed-Draw Term Loan
Debt Instrument [Line Items]
Repayments of debt											300,000,000
Bonds | PNMR 2019 Term Loan
Debt Instrument [Line Items]
Repayments of debt											150,000,000
Bonds | PNMR 2020 Term Loan
Debt Instrument [Line Items]
Repayments of debt											150,000,000
Bonds | Pollution Control Revenue Bonds Due June 2020
Debt Instrument [Line Items]
Term loans																							100,300,000
Bonds | PNM 2021 Fixed Rate PCRBs
Debt Instrument [Line Items]
Stated percentage																					0.875%
Bonds | Pollution Control Revenue Bonds, Due 2033
Debt Instrument [Line Items]
Stated percentage																					2.15%
Term loans																					$ 146,000,000		146,000,000
Bonds | Pollution Control Revenue Bonds, 1.1%, Due 2040
Debt Instrument [Line Items]
Aggregate principal amount															$ 130,000,000
Stated percentage															1.10%
Bonds | Pollution Control Revenue Bonds, 3.90%, Due 2028
Debt Instrument [Line Items]
Aggregate principal amount																	$ 130,000,000
Stated percentage																	3.90%
Bonds | PNM | Pollution Control Revenue Bonds
Debt Instrument [Line Items]
Term loans																104,500,000			$ 31,500,000
Bonds | PNM | Pollution Control Revenue Bonds Due June 2038
Debt Instrument [Line Items]
Aggregate principal amount																$ 36,000,000			36,000,000
Stated percentage																1.05%
Bonds | PNM | Pollution Control Revenue Bonds Due June 2040, 1
Debt Instrument [Line Items]
Aggregate principal amount																$ 37,000,000			$ 37,000,000
Stated percentage																2.125%
Bonds | PNM | Pollution Control Revenue Bonds Due June 2040, 2
Debt Instrument [Line Items]
Aggregate principal amount																$ 11,500,000
Stated percentage																1.20%
Bonds | PNM | Pollution Control Revenue Bonds Due June 2042
Debt Instrument [Line Items]
Aggregate principal amount																$ 20,000,000
Stated percentage																2.45%
Bonds | PNM | Pollution Control Revenue Bonds Due June 2024
Debt Instrument [Line Items]
Stated percentage																			3.00%
Bonds | TNMP | TNMP 2022 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount																				$ 160,000,000
Series of bond issuance | bond																				2
Bonds | TNMP | TNMP 2022 Bond Purchase Agreement at 4.13% Due May 12, 2022
Debt Instrument [Line Items]
Aggregate principal amount																				$ 65,000,000
Stated percentage																				4.13%
Bonds | TNMP | TNMP 2022 Bond Purchase Agreement at 3.81% Due July 28, 2032
Debt Instrument [Line Items]
Aggregate principal amount																				$ 95,000,000
Stated percentage																				3.81%
Medium-term Notes | PNMR Development Term Loan
Debt Instrument [Line Items]
Repayments of debt											$ 65,000,000
Term loans																							65,000,000
Secured Debt | PNM 2023 Term Loan
Debt Instrument [Line Items]
Aggregate principal amount		$ 500,000,000											$ 500,000,000
Variable rate													6.83%
Secured Debt | PNM | TNMP 2023 Bond Purchase Agreement
Debt Instrument [Line Items]
Series of bond issuance | bond																		2
Secured Debt | TNMP | TNMP 2021 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount									$ 65,000,000													$ 65,000,000
Stated percentage																						2.44%
Secured Debt | TNMP | TNMP 2023 Bond Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount																		$ 185,000,000
Secured Debt | TNMP | TNMP 2023 Bond Purchase Agreement , 5.01%, Due April 28, 2033
Debt Instrument [Line Items]
Aggregate principal amount																		$ 130,000,000
Stated percentage																		5.01%
Secured Debt | TNMP | TNMP 2023 Bond Purchase Agreement At 5.47%, Due July 28, 2053
Debt Instrument [Line Items]
Aggregate principal amount																		$ 55,000,000
Stated percentage																		5.47%
Senior Notes | PNM 2020 SUNs
Debt Instrument [Line Items]
Stated percentage									5.35%
Repayments of debt									$ 160,000,000
Senior Notes | PNM 2021 SUNs At 2.59 Percent Due July 15, 2033
Debt Instrument [Line Items]
Aggregate principal amount																$ 80,000,000
Stated percentage																2.59%
Senior Notes | PNM 2021 SUNs At 3.14 Percent Due July 15, 2041
Debt Instrument [Line Items]
Aggregate principal amount																$ 80,000,000
Stated percentage																3.14%
Senior Notes | PNM September 2021 Note Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount									$ 150,000,000
Senior Notes | 2.29% Senior Unsecured Notes Due December 30, 2031
Debt Instrument [Line Items]
Aggregate principal amount								$ 50,000,000
Stated percentage																2.29%
Senior Notes | 2.97% Senior Unsecured Notes Due December 30, 2041
Debt Instrument [Line Items]
Aggregate principal amount																$ 100,000,000
Stated percentage																2.97%
Notes Payable to Banks | PNM | 5.92% due April 2053
Debt Instrument [Line Items]
Aggregate principal amount										$ 75,000,000
Senior Unsecured Notes | PNM 3.15%, Senior Unsecured Notes, Due May 2023
Debt Instrument [Line Items]
Stated percentage															3.15%
Repayments of debt			$ 55,000,000
Senior Unsecured Notes | PNMR | PNMR 2018 SUNs
Debt Instrument [Line Items]
Aggregate principal amount																							$ 300,000,000
Stated percentage															3.25%
Senior Unsecured Notes | PNM | PNM 3.15%, Senior Unsecured Notes, Due May 2023
Debt Instrument [Line Items]
Aggregate principal amount															$ 55,000,000
Stated percentage															3.15%
Senior Unsecured Notes | PNM | PNM 2023 Note Purchase Agreement
Debt Instrument [Line Items]
Aggregate principal amount																		$ 200,000,000
Number of debt issuances | debtInstrument																		2
Senior Unsecured Notes | PNM | PNM 2023 SUNs At 5.15% Due April 28, 2035
Debt Instrument [Line Items]
Aggregate principal amount																		$ 150,000,000
Stated percentage																		5.51%
Senior Unsecured Notes | PNM | PNM 2023 SUNs At 5.92% Due April 28, 2053
Debt Instrument [Line Items]
Aggregate principal amount																		$ 50,000,000
Stated percentage																		5.92%
Senior Secured Notes, Energy Transition Bonds | PNM | Securitized Bonds
Debt Instrument [Line Items]
Aggregate principal amount	343,200,000
Current maturities of long-term debt														$ 2,500,000
Senior Secured Notes, Energy Transition Bonds | PNM | Securitized Bonds, 5.64%
Debt Instrument [Line Items]
Aggregate principal amount	$ 175,000,000
Stated percentage	5.64%
Senior Secured Notes, Energy Transition Bonds | PNM | Securitized Bonds, 6.03%
Debt Instrument [Line Items]
Aggregate principal amount	$ 168,200,000
Stated percentage	6.03%