Pension and Other Postretirement Benefits Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	4.00%
Public Service Company of New Mexico [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.29%	4.48%	5.27%
Discount rate for determining net periodic benefit cost (income)	4.48%	5.27%	4.30%
Expected return on plan assets	6.80%	7.20%	7.65%
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.34%	4.45%	5.21%
Discount rate for determining net periodic benefit cost (income)	4.45%	5.21%	4.26%
Expected return on plan assets	7.70%	8.50%	8.50%
Public Service Company of New Mexico [Member] | Executive Retirement Program [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.29%	4.48%	5.27%
Discount rate for determining net periodic benefit cost (income)	4.48%	5.27%	4.30%
Texas-New Mexico Power Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.39%	4.39%	5.06%
Discount rate for determining net periodic benefit cost (income)	4.39%	5.06%	4.19%
Expected return on plan assets	6.80%	7.20%	7.65%
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.34%	4.45%	5.21%
Discount rate for determining net periodic benefit cost (income)	4.45%	5.21%	4.26%
Expected return on plan assets	5.70%	6.50%	6.50%
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining PBO and APBO	5.39%	4.39%	5.06%
Discount rate for determining net periodic benefit cost (income)	4.39%	5.06%	4.19%