Income Taxes - Reconciliation of Unrecognized Tax Benefits (Expense) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, interest on income taxes expense	$ 0	$ 0	$ 0
PNMR
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	15,154,000	13,714,000	13,152,000
Additions based on tax positions		1,444,000	305,000
Reductions based on tax positions	(277,000)
Additions for tax positions of prior years	259,000		257,000
Reductions for tax positions of prior years		(4,000)
Ending balance	15,136,000	15,154,000	13,714,000
Unrecognized tax benefits that would impact effective tax rate	14,600,000
PNM
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	12,201,000	10,771,000	10,230,000
Additions based on tax positions		1,437,000	295,000
Reductions based on tax positions	(294,000)
Additions for tax positions of prior years	239,000		246,000
Reductions for tax positions of prior years		(7,000)
Ending balance	12,146,000	12,201,000	10,771,000
Unrecognized tax benefits that would impact effective tax rate	11,600,000
Unrecognized tax benefits, interest on income taxes expense	0	0	0
TNMP
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	151,000	141,000	119,000
Additions based on tax positions	17,000	7,000	11,000
Additions for tax positions of prior years	20,000	3,000	11,000
Ending balance	188,000	151,000	141,000
Unrecognized tax benefits that would impact effective tax rate	200,000
Unrecognized tax benefits, interest on income taxes expense	$ 0	$ 0	$ 0