Pension and Other Postretirement Benefits Pre-Tax Information about Prior Service Cost and Net Actuarial (Gain) loss in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Public Service Company of New Mexico [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit) - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	$ (1,855)	$ (2,260)
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	146,775	148,212
Prior service cost (credit) - Experience loss (gain)	0
Net actuarial (gain) loss - Experience loss (gain)	11,397
Prior service cost (credit) - Regulatory asset (liability) adjustment	0
Net actuarial (gain) loss - Regulatory asset (liability) adjustment	(6,610)
Prior service cost (credit) - Amortization recognized in net periodic benefit cost (income)	405
Net actuarial (gain) loss - Amortization recognized in net periodic benefit cost (income)	(6,224)
Prior service cost (credit) - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	(1,855)	(2,260)
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	146,775	148,212
Prior service cost (credit) - Amortization expected to be recognized in in 2015	(405)
Net actuarial (gain) loss - Amortization expected to be recognized in in 2015	5,399
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss - Experience loss (gain)	(300)
Public Service Company of New Mexico [Member] | Executive Retirement Program [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	2,084	2,602
Net actuarial (gain) loss - Experience loss (gain)	(908)
Net actuarial (gain) loss - Regulatory asset (liability) adjustment	526
Net actuarial (gain) loss - Amortization recognized in net periodic benefit cost (income)	(136)
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	2,084	2,602
Net actuarial (gain) loss - Amortization expected to be recognized in in 2015	108
Texas-New Mexico Power Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	0	0
Net actuarial (gain) loss - Experience loss (gain)	365
Net actuarial (gain) loss - Regulatory asset (liability) adjustment	(365)
Net actuarial (gain) loss - Amortization recognized in net periodic benefit cost (income)	0
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	0	0
Net actuarial (gain) loss - Amortization expected to be recognized in in 2015	0
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss - Experience loss (gain)	100
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	0	0
Net actuarial (gain) loss - Experience loss (gain)	26
Net actuarial (gain) loss - Regulatory asset (liability) adjustment	(26)
Net actuarial (gain) loss - Amortization recognized in net periodic benefit cost (income)	0
Net actuarial (gain) loss - Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	0	$ 0
Net actuarial (gain) loss - Amortization expected to be recognized in in 2015	$ 0