Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Percentage of Pension Liability Adjustment Capitalized into Construciton Work In Process			16.40%
Percentage of Pension Liability Adjustment Capitalized into Other Accounts			2.50%
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	$ (78,594)		$ (81,630)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			(3,573)
Income tax impact of amounts reclassified from accumulated other comprehensive income			1,417
Other Comprehensive Income (Loss), before Reclassifications, before Tax			8,594
Other Comprehensive Income (Loss), Tax			(3,402)
Other Comprehensive Income (Loss), Net of Tax	(1,903)	(2,322)	3,036	4,228
Balance at March 31, 2013	(78,594)		(78,594)
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			(6,854)
Income tax impact of amounts reclassified from accumulated other comprehensive income			2,714
Other Comprehensive Income (Loss), before Reclassifications, before Tax			8,591
Other Comprehensive Income (Loss), Tax			(3,401)
Other Comprehensive Income (Loss), Net of Tax			1,050
Balance at March 31, 2013	17,456		17,456
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			3,182
Income tax impact of amounts reclassified from accumulated other comprehensive income			(1,262)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			0
Other Comprehensive Income (Loss), Tax			0
Other Comprehensive Income (Loss), Net of Tax			1,920
Balance at March 31, 2013	(95,900)		(95,900)
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			99
Income tax impact of amounts reclassified from accumulated other comprehensive income			(35)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			3
Other Comprehensive Income (Loss), Tax			(1)
Other Comprehensive Income (Loss), Net of Tax			66
Balance at March 31, 2013	(150)		(150)
Public Service Company of New Mexico [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(78,444)		(81,414)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			(3,672)
Income tax impact of amounts reclassified from accumulated other comprehensive income			1,452
Other Comprehensive Income (Loss), before Reclassifications, before Tax			8,591
Other Comprehensive Income (Loss), Tax			(3,401)
Other Comprehensive Income (Loss), Net of Tax	(1,930)	(2,279)	2,970	4,350
Balance at March 31, 2013	(78,444)		(78,444)
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			(6,854)
Income tax impact of amounts reclassified from accumulated other comprehensive income			2,714
Other Comprehensive Income (Loss), before Reclassifications, before Tax			8,591
Other Comprehensive Income (Loss), Tax			(3,401)
Other Comprehensive Income (Loss), Net of Tax			1,050
Balance at March 31, 2013	17,456		17,456
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			3,182
Income tax impact of amounts reclassified from accumulated other comprehensive income			(1,262)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			0
Other Comprehensive Income (Loss), Tax			0
Other Comprehensive Income (Loss), Net of Tax			1,920
Balance at March 31, 2013	(95,900)		(95,900)
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		0
Texas-New Mexico Power Company [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(150)		(216)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax			99
Income tax impact of amounts reclassified from accumulated other comprehensive income			(35)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			3
Other Comprehensive Income (Loss), Tax			(1)
Other Comprehensive Income (Loss), Net of Tax	27	(43)	66	(122)
Balance at March 31, 2013	(150)		(150)
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		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		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			99
Income tax impact of amounts reclassified from accumulated other comprehensive income			(35)
Other Comprehensive Income (Loss), before Reclassifications, before Tax			3
Other Comprehensive Income (Loss), Tax			(1)
Other Comprehensive Income (Loss), Net of Tax			66
Balance at March 31, 2013	$ (150)		$ (150)