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Fair Value of Derivative and Other Financial Instruments - Maturities of Securities (Details) - PNMR and PNM $ in Thousands	Dec. 31, 2020 USD ($)
Available-for-Sale
Within 1 year	$ 33,301
After 1 year through 5 years	89,646
After 5 years through 10 years	89,130
After 10 years through 15 years	14,947
After 15 years through 20 years	9,256
After 20 years	43,730
Debt securities, available-for-sale	$ 280,010

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- Definition

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

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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