Revenues Alternative Revenue Programs (Policies)	3 Months Ended
Revenues Alternative Revenue Programs (Policies)	Mar. 31, 2018
Revenue Recognition [Abstract]
Revenue Recognition for Alternative Revenue Programs, Policy	alternative revenue program revenue relating to the Company’s potential bonus awards from the PUCT and the NMPRC mandated energy efficiency programs. Both the PUCT and the NMPRC allow for the potential to earn an incentive bonus if the Company achieves its approved energy efficiency goals under the applicable programs. The Company recognizes revenue related to the energy efficiency program incentives at the point in time that the amount is objectively determinable generally based upon an approved order from the regulator, is probable of recovery, and if it is expected to be collected within 24 months.

Disclosure of accounting policy for revenue recognition related to alternative revenue programs. The major alternative revenue programs can generally be segregated into two categories, programs that adjust billings for the effects of weather abnormalities or broad external factors or to compensate the utility for demand-side management initiatives (for example, no-growth plans and similar conservation efforts); and programs that provide for additional billings (incentive awards) if the utility achieves certain objectives, such as reducing costs, reaching specified milestones, or demonstratively improving customer service.