Pension and Other Postretirement Benefits Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	4.00%
Amortization of gains and losses that are outside the corridor	5 years
Maximum annual contributions per employee	75.00%
Employer matching contribution, percent of employees' gross pay	6.00%
Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-matching contribution of eligible compensation based on eligible employee's age	3.00%
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Non-matching contribution of eligible compensation based on eligible employee's age	10.00%
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term return resulting from effect of 1% change	1.00%
Expected long-term return resulting from effect of one-percentage point increase (as a percent)	1.00%
Expected employer contributions to pension plans	$ 0
Pension Plan [Member] | Minimum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate related to anticipated contributions	4.80%
Pension Plan [Member] | Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate related to anticipated contributions	5.70%
Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	21.00%
Pension Plan [Member] | Equity Securities [Member] | Developed Countries Outside of United States [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	6.00%
Pension Plan [Member] | Debt Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	65.00%
Pension Plan [Member] | Alternative Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	14.00%
Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected long-term return resulting from effect of 1% change	1.00%
Other Postretirement Benefits [Member] | Equity Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	70.00%
Other Postretirement Benefits [Member] | Debt Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target plan asset allocations	30.00%
Public Service Company of New Mexico [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	6.80%	7.20%	7.65%
Defined benefit plan, other changes	$ (45,900,000)	$ 50,600,000
Actuarial gain (loss) resulting from changes in demographics and other trends	(2,800,000)	(200,000)
Actuarial gain (loss) resulting from changes in other assumptions and experience	(4,900,000)	200,000
Increased PBO		$ 21,900,000
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	$ 5,400,000
Actual rate of return for pension plans	(1.70%)
Actuarial gains (losses) recorded as regulatory assets	$ (11,397,000)
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	7.70%	8.50%	8.50%
Defined benefit plan, other changes	$ (7,300,000)	$ 6,700,000
Actuarial gain (loss) resulting from changes in demographics and other trends	(700,000)	5,400,000
Increased PBO		$ 3,200,000
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	$ 700,000
Actual rate of return for pension plans	(0.80%)
Actuarial gains (losses) recorded as regulatory assets	$ 300,000
Estimated future employer contributions in next fiscal year	3,500,000
Estimated future employer contributions in years two through five	$ 14,000,000
Texas-New Mexico Power Company [Member] | Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	6.80%	7.20%	7.65%
Defined benefit plan, other changes	$ (6,100,000)	$ 5,100,000
Actuarial gain (loss) resulting from changes in demographics and other trends	(900,000)	400,000
Actuarial gain (loss) resulting from changes in other assumptions and experience	(100,000)	(1,300,000)
Increased PBO		$ 2,500,000
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	$ 600,000
Actual rate of return for pension plans	(1.70%)
Actuarial gains (losses) recorded as regulatory assets	$ (365,000)
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets	5.70%	6.50%	6.50%
Defined benefit plan, other changes	$ (1,300,000)	$ 1,100,000
Actuarial gain (loss) resulting from changes in demographics and other trends	(700,000)	(100,000)
Increased PBO		$ 500,000
Expected long-term return on assets decrease resulting in increase net periodic costs In next fiscal year	$ 100,000
Actual rate of return for pension plans	(0.50%)
Actuarial gains (losses) recorded as regulatory assets	$ (100,000)
Effect of 1%-point change in assumed health care cost trend rates on net periodic expense and APBO	0
Estimated future employer contributions in next fiscal year	300,000
Estimated future employer contributions in years two through five	$ 1,400,000