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Fair Value of Derivative and Other Financial Instruments - Maturities of Debt Securities (Details) - PNMR and PNM $ in Thousands	Sep. 30, 2019 USD ($)
Available-for-Sale
Within 1 year	$ 28,015
After 1 year through 5 years	79,195
After 5 years through 10 years	65,492
After 10 years through 15 years	13,960
After 15 years through 20 years	9,598
After 20 years	39,894
Available-for-sale debt securities	$ 236,154

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- Definition

Available-for-sale Securities, Debt Maturities, after Fifteen Years Through Twenty Years, Fair Value

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