Pension and Other Postretirement Benefit Plans (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension liability, Estimated percentage increase due to change in assumptions	7.00%		7.00%
Public Service Company of New Mexico [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	7,541,000	7,035,000	22,622,000	21,106,000
Expected return on plan assets	(9,511,000)	(10,482,000)	(28,533,000)	(31,447,000)
Amortization of net (gain) loss	3,255,000	3,710,000	9,765,000	11,130,000
Amortization of prior service cost	(241,000)	19,000	(724,000)	57,000
Net Periodic Benefit Cost (Income)	1,044,000	282,000	3,130,000	846,000
Defined Benefit Plan, Contributions by Employer		0		60,000,000
Defined Benefit Plan, Estimated Future Employer Contributions After Current Fiscal Year	50,000,000		50,000,000
Public Service Company of New Mexico [Member] | Pension Plan [Member] | Minimum [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate (as a percent)			4.50%
Public Service Company of New Mexico [Member] | Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate (as a percent)			5.30%
Public Service Company of New Mexico [Member] | OPEB [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	45,000	65,000	136,000	195,000
Interest cost	1,159,000	1,029,000	3,473,000	3,085,000
Expected return on plan assets	(1,410,000)	(1,261,000)	(4,229,000)	(3,782,000)
Amortization of net (gain) loss	556,000	1,061,000	1,669,000	3,182,000
Amortization of prior service cost	(336,000)	(336,000)	(1,008,000)	(1,008,000)
Net Periodic Benefit Cost (Income)	14,000	558,000	41,000	1,672,000
Defined Benefit Plan, Contributions by Employer	800,000	800,000	2,400,000	2,400,000
Defined Benefit Plan, Estimated Future Employer Contributions After Current Fiscal Year	14,000,000		14,000,000
Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year	3,300,000		3,300,000
Public Service Company of New Mexico [Member] | Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0	0
Interest cost	205,000	180,000	616,000	540,000
Expected return on plan assets	0	0	0	0
Amortization of net (gain) loss	52,000	58,000	157,000	174,000
Amortization of prior service cost	0	0	0	0
Net Periodic Benefit Cost (Income)	257,000	238,000	773,000	714,000
Defined Benefit Plan, Contributions by Employer	400,000	400,000	1,200,000	1,100,000
Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year	1,600,000		1,600,000
Texas-New Mexico Power Company [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0	0
Interest cost	798,000	772,000	2,395,000	2,315,000
Expected return on plan assets	(1,132,000)	(1,212,000)	(3,395,000)	(3,637,000)
Amortization of net (gain) loss	166,000	262,000	499,000	787,000
Amortization of prior service cost	0	0	0	0
Net Periodic Benefit Cost (Income)	(168,000)	(178,000)	(501,000)	(535,000)
Defined Benefit Plan, Contributions by Employer		0		1,000,000
Defined Benefit Plan, Estimated Future Employer Contributions After Current Fiscal Year	0		0
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | Minimum [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate (as a percent)	4.50%
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate (as a percent)	5.30%
Texas-New Mexico Power Company [Member] | OPEB [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	59,000	75,000	178,000	225,000
Interest cost	155,000	141,000	464,000	424,000
Expected return on plan assets	(133,000)	(126,000)	(400,000)	(377,000)
Amortization of net (gain) loss	(31,000)	0	(92,000)	0
Amortization of prior service cost	8,000	14,000	24,000	43,000
Net Periodic Benefit Cost (Income)	58,000	104,000	174,000	315,000
Defined Benefit Plan, Contributions by Employer	0	0	300,000	300,000
Defined Benefit Plan, Estimated Future Employer Contributions After Current Fiscal Year	1,400,000		1,400,000
Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year	300,000		300,000
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0	0
Interest cost	10,000	9,000	29,000	27,000
Expected return on plan assets	0	0	0	0
Amortization of net (gain) loss	0	0	0	0
Amortization of prior service cost	0	0	0	0
Net Periodic Benefit Cost (Income)	10,000	9,000	29,000	27,000
Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year	100,000		100,000
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member] | Maximum [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Contributions by Employer	$ 100,000	$ 100,000	$ 100,000	$ 100,000