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Significant Accounting Policies and Responsibility for Financial Statements (Details) - USD ($)	1 Months Ended		3 Months Ended
	Mar. 31, 2021	Feb. 29, 2020	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Payment defaults under agreements	$ 0		$ 0
Dividends declared per common share (dollars per share)	$ 0.3275	$ 0.3075	$ 0.3275	$ 0.3075
Dividends declared on common stock			$ 28,111,000	$ 24,493,000
PNM
Business Acquisition [Line Items]
Dividends declared on common stock				40,654,000
Texas-New Mexico Power Company
Business Acquisition [Line Items]
Dividends declared on common stock				$ 11,347,000

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- Definition

Collaborative Arrangement, Owner Obligations, Default, Amount

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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-Topic 505
-SubTopic 10
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