Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Earnings Attributable to PNMR	$ 73,739	$ 54,418	$ 134,156	$ 92,040
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)	284	96	215	99
Average Shares – Basic (in shares)	79,938	79,750	79,869	79,753
Dilutive Effect of Common Stock Equivalents:
Stock options and restricted stock (in shares)	216	367	263	377
Average Shares – Diluted (in shares)	80,154	80,117	80,132	80,130
Net Earnings Per Share of Common Stock:
Basic (in dollars per share)	$ 0.92	$ 0.68	$ 1.68	$ 1.15
Diluted (in dollars per share)	$ 0.92	$ 0.68	$ 1.67	$ 1.15