Stockholders' Equity (Details) - USD ($)		12 Months Ended
	Dec. 15, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 07, 2020
Class of Stock [Line Items]
Payment of dividends		$ 404,700,000
PNMR 2020 Forward Equity Sales Agreement
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)	6,200,000
Sale of stock, price per share (in dollars per share)	$ 45.805				$ 47.21
Sale of stock, consideration received on transaction	$ 283,100,000
Payments of stock issuance costs	$ 100,000
Line of Credit
Class of Stock [Line Items]
Debt-to-capital ratio (not more than)		70.00%
Public Service Company of New Mexico
Class of Stock [Line Items]
Equity contribution from parent		$ 53,000,000	$ 230,000,000	$ 0
Requirement to obtain approval to transfer more than a percentage of PNM's assets		5.00%
Preferred stock, dividend rate		4.58%
Preferred stock, redemption percent		102.00%
Preferred stock outstanding (in shares)		115,293	115,293
Preferred stock, cumulative shares authorized (in shares)		10,000,000	10,000,000
Public Service Company of New Mexico | Line of Credit
Class of Stock [Line Items]
Debt-to-capital ratio (not more than)		65.00%
Public Service Company of New Mexico | Affiliated Entity
Class of Stock [Line Items]
Cash dividends paid to parent company by consolidated subsidiaries		$ 60,000,000	$ 40,700,000	0
Texas-New Mexico Power Company
Class of Stock [Line Items]
Equity contribution from parent		$ 52,000,000	71,000,000	80,000,000
Preferred stock, cumulative shares authorized (in shares)		1,000,000
Texas-New Mexico Power Company | Line of Credit
Class of Stock [Line Items]
Debt-to-capital ratio (not more than)		65.00%
Texas-New Mexico Power Company | Affiliated Entity
Class of Stock [Line Items]
Cash dividends paid to parent company by consolidated subsidiaries		$ 0	$ 58,500,000	$ 55,300,000
PNMR and TNMP
Class of Stock [Line Items]
Preferred stock outstanding (in shares)		0