Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 68,311	$ 16,154	$ 70,226
Amortization of accumulated investment tax credits	(973)	(1,342)	(2,164)
Flow-through of depreciation items	1,227	1,485	1,344
Earnings attributable to non-controlling interest in Valencia	(5,082)	(5,218)	(4,945)
State income tax, net of federal benefit	4,537	(1,781)	5,723
Impairment of state net operating loss carryforwards	(311)	5,278	3,129
Impairment of state production tax credits	0	3,092	894
Allowance for equity funds used during construction	(1,732)	(3,650)	(1,947)
Reversal of deferred items related to BART at SJGS	0	1,826	0
Impairment of charitable contribution carryforward	0	2,042	0
Regulatory recovery of prior year impairment of state net operating loss carryforward, net of amortization	(1,877)	0	0
Other	(822)	(2,811)	(2,522)
Total income taxes (benefit)	$ 63,278	$ 15,075	$ 69,738
Effective tax rate	32.42%	32.66%	34.76%
Public Service Company of New Mexico [Member]
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 46,501	$ (4,579)	$ 53,930
Amortization of accumulated investment tax credits	(973)	(1,342)	(2,164)
Flow-through of depreciation items	1,185	1,465	1,325
Earnings attributable to non-controlling interest in Valencia	(5,082)	(5,218)	(4,945)
State income tax, net of federal benefit	3,921	(2,162)	5,522
Impairment of state net operating loss carryforwards	(213)	3,619	2,145
Allowance for equity funds used during construction	(1,457)	(3,650)	(1,947)
Reversal of deferred items related to BART at SJGS	0	1,826	0
Impairment of charitable contribution carryforward	(301)	(737)	(737)
Regulatory recovery of prior year impairment of state net operating loss carryforward, net of amortization	(1,877)	0	0
Other	(782)	(1,980)	(496)
Total income taxes (benefit)	$ 40,922	$ (12,758)	$ 52,633
Effective tax rate	30.80%	97.52%	34.16%
Texas-New Mexico Power Company [Member]
Income Taxes [Line Items]
Federal income tax at statutory rates	$ 22,928	$ 23,131	$ 21,115
State income tax, net of federal benefit	1,132	1,065	1,257
Other	(224)	(71)	151
Total income taxes (benefit)	$ 23,836	$ 24,125	$ 22,523
Effective tax rate	36.39%	36.50%	37.33%