Merger	12 Months Ended
Merger	Dec. 31, 2020
Business Combinations [Abstract]
Merger	Merger On October 20, 2020, PNMR, Avangrid, and Merger Sub, entered into the Merger Agreement pursuant to which Merger Sub will merge with and into PNMR, with PNMR surviving the Merger as a wholly-owned subsidiary of Avangrid. Pursuant to the Merger Agreement, each issued and outstanding share of the common stock of PNMR (other than (i) the issued shares of PNMR common stock that are owned by Avangrid, Merger Sub, PNMR or any wholly-owned subsidiary of Avangrid or PNMR, which will be automatically cancelled at the time the Merger is consummated (the "Effective Time") and (ii) shares of PNMR common stock outstanding immediately prior to the Effective Time and held by a holder who has not voted in favor of, or consented in writing to, the Merger who is entitled to, and who has demanded, payment for fair value of such shares) will be converted into the right to receive $50.30 in cash. The proposed Merger has been unanimously approved by the Boards of Directors of PNMR, Avangrid and Merger Sub and approved by PNMR shareholders at the Special Meeting of Shareholders held on February 12, 2021. On January 20, 2021, the FTC notified PNMR and Avangrid that early termination of the waiting period under the HSR Act in connection with the Merger was granted. CFIUS completed its review of the Merger on February 2, 2021, and has concluded that there are no unresolved national security concerns with respect to the Merger. The early termination of the waiting period under the HSR Act and clearance by CFIUS satisfies two of the conditions to the closing of the transactions contemplated by the Merger Agreement. Consummation of the Merger remains subject to the satisfaction or waiver of certain customary closing conditions, including, without limitation, the absence of any material adverse effect on PNMR, the receipt of required regulatory approvals (including the PUCT, the NMPRC, FERC, the FCC, and the NRC) and the agreements relating to the divestiture of Four Corners being in full force and effect and all applicable regulatory filings associated therewith being made. The Merger is currently expected to close in the second half of 2021. In connection with the Merger, Iberdrola, S.A. a corporation organized under the laws of the Kingdom of Spain, which owns 81.5% of the outstanding common stock of Avangrid (“Iberdrola”), has provided Avangrid a commitment letter (the "Iberdrola Funding Commitment Letter"), pursuant to which Iberdrola has unilaterally agreed to provide to Avangrid, or arrange the provision to Avangrid of, funds to the extent necessary for Avangrid to consummate the Merger, including the payment of the aggregate Merger consideration. To the extent Avangrid wishes to effect a funding transaction under the Iberdrola Funding Commitment Letter in order to pay the Merger consideration, the specific terms of any such transaction will be negotiated between Iberdrola and Avangrid on an arm's length basis and must be approved by both (i) a majority of the members of the unaffiliated committee of the board of directors of Avangrid, and (ii) the entire board of directors of Avangrid. Under the terms of such commitment letter, Iberdrola has agreed to negotiate with Avangrid the specific terms of any transaction effecting such funding commitment promptly and in good faith, with the objective that such terms shall be commercially reasonable and approved by Avangrid. Avangrid’s and Merger Sub’s obligations under the Merger Agreement are not conditioned upon Avangrid obtaining financing. The Merger Agreement provides for certain customary termination rights including the right of either party to terminate the Merger Agreement if the Merger is not completed on or before January 20, 2022 (subject to a three-month extension by either party if all of the conditions to the closing, other than the conditions related to obtaining regulatory approvals, have been satisfied or waived). The Merger Agreement further provides that, upon termination of the Merger Agreement under certain specified circumstances (including if Avangrid terminates the Merger Agreement due to a change in recommendation of the Board or if PNMR terminates the Merger Agreement to accept a superior proposal (as defined in the Merger Agreement)), PNMR will be required to pay Avangrid a termination fee of $130.0 million. In addition, the Merger Agreement provides that (i) if the Merger Agreement is terminated by either party due to a failure of a regulatory closing condition and such failure is the result of Avangrid’s breach of its regulatory covenants, or (ii) Avangrid fails to effect the closing when all closing conditions have been satisfied and it is otherwise obligated to do so under the Merger Agreement, then, in either such case, upon termination of the Merger Agreement, Avangrid will be required to pay PNMR a termination fee of $184.0 million as the sole and exclusive remedy. Upon the termination of the Merger Agreement under certain specified circumstances involving a breach of the Merger Agreement, either PNMR or Avangrid will be required to reimburse the other party’s reasonable and documented out-of-pocket fees and expenses up to $10.0 million (which amount will be credited toward, and offset against, the payment of any applicable termination fee).