Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Earnings Attributable to PNMR	$ 121,768	$ 102,771	$ 163,997	$ 45,557
Average Number of Common Shares:
Outstanding during period (in shares)	79,654	79,654	79,654	79,654
Vested awards of restricted stock (in shares)	213	294	205	265
Average Shares – Basic (in shares)	79,867	79,948	79,859	79,919
Dilutive Effect of Common Stock Equivalents:
PNMR 2020 Forward Equity Sale Agreements (in shares)	0	0	57	0
Restricted stock (in shares)	39	53	38	61
Average Shares – Diluted (in shares)	79,906	80,001	79,954	79,980
Net Earnings Per Share of Common Stock:
Basic (in dollars per share)	$ 1.52	$ 1.29	$ 2.05	$ 0.57
Diluted (in dollars per share)	$ 1.52	$ 1.28	$ 2.05	$ 0.57