Fair Value Measures and Disclosures - Gross Realized (Losses) (Details) - PNM - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Proceeds from sales	$ 137,797	$ 92,371	$ 412,574	$ 323,251
Gross realized gains	4,022	2,366	14,464	20,089
Gross realized (losses)	$ (6,876)	$ (6,908)	$ (19,088)	$ (23,109)