Fair Value of Derivative and Other Financial Instruments - Investment in NDT and Gross Realized Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity securities:
Net gains (losses) from equity securities sold	$ (6,940)	$ 8,738	$ 5,861
Net gains (losses) from equity securities still held	(38,025)	(442)	17,707
Total net gains (losses) on equity securities	(44,965)	8,296	23,568
Available-for-sale debt securities:
Net gains (losses) on debt securities	(33,392)	8,554	(1,969)
Net gains (losses) on investment securities	(78,357)	16,850	21,599
Public Service Company of New Mexico
Available-for-sale debt securities:
Proceeds from sales	526,448	459,867	590,998
Gross realized gains	22,071	39,408	35,904
Gross realized (losses)	$ (36,623)	$ (22,815)	$ (28,817)

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