Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Equity [Abstract]
Percentage of Pension Liability Adjustment Capitalized into Construciton Work In Process	15.00%
Percentage of Pension Liability Adjustment Capitalized into Other Accounts	2.50%
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	$ (81,630)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	303
Income tax impact of amounts reclassified from accumulated other comprehensive income	(119)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	7,870
Other Comprehensive Income (Loss), Tax	(3,115)
Other Comprehensive Income (Loss), Net of Tax	4,939	6,551
Balance at March 31, 2013	(76,691)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	16,406
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(1,336)
Income tax impact of amounts reclassified from accumulated other comprehensive income	529
Other Comprehensive Income (Loss), before Reclassifications, before Tax	7,858
Other Comprehensive Income (Loss), Tax	(3,111)
Other Comprehensive Income (Loss), Net of Tax	3,940
Balance at March 31, 2013	20,346
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(97,820)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1,591
Income tax impact of amounts reclassified from accumulated other comprehensive income	(631)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0
Other Comprehensive Income (Loss), Tax	0
Other Comprehensive Income (Loss), Net of Tax	960
Balance at March 31, 2013	(96,860)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(216)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	48
Income tax impact of amounts reclassified from accumulated other comprehensive income	(17)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	12
Other Comprehensive Income (Loss), Tax	(4)
Other Comprehensive Income (Loss), Net of Tax	39
Balance at March 31, 2013	(177)
Public Service Company of New Mexico [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(81,414)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	255
Income tax impact of amounts reclassified from accumulated other comprehensive income	(102)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	7,858
Other Comprehensive Income (Loss), Tax	(3,111)
Other Comprehensive Income (Loss), Net of Tax	4,900	6,630
Balance at March 31, 2013	(76,514)
Public Service Company of New Mexico [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	16,406
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(1,336)
Income tax impact of amounts reclassified from accumulated other comprehensive income	529
Other Comprehensive Income (Loss), before Reclassifications, before Tax	7,858
Other Comprehensive Income (Loss), Tax	(3,111)
Other Comprehensive Income (Loss), Net of Tax	3,940
Balance at March 31, 2013	20,346
Public Service Company of New Mexico [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(97,820)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	1,591
Income tax impact of amounts reclassified from accumulated other comprehensive income	(631)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0
Other Comprehensive Income (Loss), Tax	0
Other Comprehensive Income (Loss), Net of Tax	960
Balance at March 31, 2013	(96,860)
Public Service Company of New Mexico [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0
Income tax impact of amounts reclassified from accumulated other comprehensive income	0
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0
Other Comprehensive Income (Loss), Tax	0
Other Comprehensive Income (Loss), Net of Tax	0
Balance at March 31, 2013	0
Texas-New Mexico Power Company [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(216)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	48
Income tax impact of amounts reclassified from accumulated other comprehensive income	(17)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	12
Other Comprehensive Income (Loss), Tax	(4)
Other Comprehensive Income (Loss), Net of Tax	39	(79)
Balance at March 31, 2013	(177)
Texas-New Mexico Power Company [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0
Income tax impact of amounts reclassified from accumulated other comprehensive income	0
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0
Other Comprehensive Income (Loss), Tax	0
Other Comprehensive Income (Loss), Net of Tax	0
Balance at March 31, 2013	0
Texas-New Mexico Power Company [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0
Income tax impact of amounts reclassified from accumulated other comprehensive income	0
Other Comprehensive Income (Loss), before Reclassifications, before Tax	0
Other Comprehensive Income (Loss), Tax	0
Other Comprehensive Income (Loss), Net of Tax	0
Balance at March 31, 2013	0
Texas-New Mexico Power Company [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(216)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	48
Income tax impact of amounts reclassified from accumulated other comprehensive income	(17)
Other Comprehensive Income (Loss), before Reclassifications, before Tax	12
Other Comprehensive Income (Loss), Tax	(4)
Other Comprehensive Income (Loss), Net of Tax	39
Balance at March 31, 2013	$ (177)