Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating loss	$ 160,901	$ 161,691
Regulatory liabilities related to income taxes	64,657	80,031
Federal tax credit carryforwards	78,675	77,417
Shutdown of SJGS Units 2 and 3	53,434	53,823
Other	75,805	70,749
Total deferred tax assets	433,472	443,711
Deferred tax liabilities:
Depreciation and plant related	(1,102,458)	(1,027,047)
Investment tax credit	(56,017)	(56,589)
Regulatory assets related to income taxes	(66,378)	(71,054)
CTC	(12,715)	(16,151)
Pension	(57,287)	(65,226)
Other	(79,267)	(85,037)
Total deferred tax liabilities	(1,374,122)	(1,321,104)
Current accumulated deferred income tax (asset) liability	(940,650)	(877,393)
Public Service Company of New Mexico [Member]
Deferred tax assets:
Net operating loss	117,922	116,693
Regulatory liabilities related to income taxes	60,940	75,889
Federal tax credit carryforwards	59,156	57,928
Shutdown of SJGS Units 2 and 3	53,434	53,823
Other	41,700	41,210
Total deferred tax assets	333,152	345,543
Deferred tax liabilities:
Depreciation and plant related	(891,578)	(828,926)
Investment tax credit	(56,017)	(56,589)
Regulatory assets related to income taxes	(56,577)	(61,018)
Pension	(50,134)	(58,070)
Other	(27,512)	(37,324)
Total deferred tax liabilities	(1,081,818)	(1,041,927)
Current accumulated deferred income tax (asset) liability	(748,666)	(696,384)
Texas-New Mexico Power Company [Member]
Deferred tax assets:
Regulatory liabilities related to income taxes	3,718	4,141
Other	6,016	6,702
Total deferred tax assets	9,734	10,843
Deferred tax liabilities:
Depreciation and plant related	(201,017)	(189,322)
Regulatory assets related to income taxes	(9,800)	(10,036)
Loss on reacquired debt	(11,937)	(12,392)
CTC	(12,715)	(16,151)
Other	(20,050)	(15,733)
Total deferred tax liabilities	(255,519)	(243,634)
Current accumulated deferred income tax (asset) liability	$ (245,785)	$ (232,791)