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Summary of the Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

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,
			2020						2019						2018
PNM
Electric plant			2.47		%				2.47		%				2.40		%
Common, intangible, and general plant			7.65		%				7.91		%				8.18		%
TNMP			3.95		%				4.04		%				3.49		%

Schedule of Inventory

Inventories consisted of the following at December 31:

			PNMR												PNM												TNMP
			2020						2019						2020						2019						2020						2019
			(In thousands)
Coal			$	12,012					$	24,914					$	12,012					$	24,914					$	—					$	—
Materials and supplies			54,405						53,015						48,460						47,311						5,945						5,704
			$	66,417					$	77,929					$	60,472					$	72,225					$	5,945					$	5,704

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Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

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