Summary of the Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Schedule of Average Rates Used Allocated Between Depreciation Expense and Construction Expense Projects Based on Use of Equipment

Average straight-line rates used were as follows:

	Year ended December 31,
	2021		2020		2019
PNM
Electric plant	2.48	%	2.47	%	2.47	%
Common, intangible, and general plant	7.91	%	7.65	%	7.91	%
TNMP	3.88	%	3.95	%	4.04	%

Schedule of Inventory

Inventories consisted of the following at December 31:

	PNMR				PNM				TNMP
	2021		2020		2021		2020		2021		2020
	(In thousands)
Coal	$	2,973	$	12,012	$	2,973	$	12,012	$	—	$	—
Materials and supplies	62,088		54,405		54,969		48,460		7,119		5,945
	$	65,061	$	66,417	$	57,942	$	60,472	$	7,119	$	5,945