Pension and Other Postretirement Benefits Components of Net Periodic Benefit Cost (Income) Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Public Service Company of New Mexico [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	28,255	30,163	28,142
Expected return on plan assets	(39,323)	(38,044)	(41,930)
Amortization of net (gain) loss	14,820	13,020	14,840
Amortization of prior service cost	(965)	(965)	76
Net periodic benefit cost	2,787	4,174	1,128
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	204	181	260
Interest cost	4,089	4,630	4,113
Expected return on plan assets	(5,610)	(5,638)	(5,043)
Amortization of net (gain) loss	1,966	2,225	4,242
Amortization of prior service cost	(642)	(1,343)	(1,343)
Net periodic benefit cost	7	55	2,229
Public Service Company of New Mexico [Member] | Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	760	822	720
Amortization of net (gain) loss	325	210	232
Amortization of prior service cost	0	0	0
Net periodic benefit cost	1,085	1,032	952
Texas-New Mexico Power Company [Member] | Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	3,043	3,193	3,087
Expected return on plan assets	(4,420)	(4,526)	(4,849)
Amortization of net (gain) loss	782	665	1,049
Amortization of prior service cost	0	0	0
Net periodic benefit cost	(595)	(668)	(713)
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	247	237	299
Interest cost	608	619	566
Expected return on plan assets	(520)	(534)	(503)
Amortization of net (gain) loss	0	(122)	0
Amortization of prior service cost	0	32	57
Net periodic benefit cost	335	232	419
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0
Interest cost	36	39	36
Amortization of net (gain) loss	5	0	0
Amortization of prior service cost	0	0	0
Net periodic benefit cost	$ 41	$ 39	$ 36