Construction Program and Jointly-Owned Electric Generating Plants - Construction Program and Jointly-Owned Electric Generating Plants (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) generating_unit	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	$ 600,076	$ 558,589	$ 460,658
Plant in Service	6,944,534	6,307,261
Accumulated Depreciation	(2,334,938)	(2,058,772)
Regulatory disallowance	$ 15,011	167,471	1,062
Operating lease, option term extensions	2 years
Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	$ 445,464	404,840	316,800
Plant in Service	5,359,211	4,833,303
Accumulated Depreciation	(1,809,528)	(1,569,549)
Regulatory disallowance	15,011	167,471	1,062
Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member]
Jointly Owned Utility Plant Interests [Line Items]
Regulatory disallowance		21,600
Texas-New Mexico Power Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	122,518	124,584	$ 127,191
Plant in Service	1,380,584	1,285,727
Accumulated Depreciation	(429,397)	(406,516)
Joint Projects [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	445,500
Joint Projects [Member] | Texas-New Mexico Power Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	122,500
Joint Projects [Member] | PNMR [Member]
Jointly Owned Utility Plant Interests [Line Items]
Construction expenditures	$ 600,100
SJGS (Coal) [Member] | Unit 3 [Member] | Other Unrelated Entities 1 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	41.80%
SJGS (Coal) [Member] | Unit 3 [Member] | Other Unrelated Entities 2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Composite Interest	8.20%
SJGS (Coal) [Member] | Unit 4 [Member] | Other Unrelated Entities 3 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	28.80%
SJGS (Coal) [Member] | Unit 4 [Member] | Other Unrelated Entities 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	10.04%
SJGS (Coal) [Member] | Unit 4 [Member] | Other Unrelated Entities 5 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	8.475%
SJGS (Coal) [Member] | Unit 4 [Member] | Other Unrelated Entities 6 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	7.20%
SJGS (Coal) [Member] | Unit 4 [Member] | Other Unrelated Entities 7 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership percentage	7.028%
SJGS (Coal) [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 1,082,537
Accumulated Depreciation	(445,597)
Construction Work in Progress	$ 4,406
Composite Interest	46.30%
SJGS (Coal) [Member] | Public Service Company of New Mexico [Member] | Unit 3 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Composite Interest	50.00%
SJGS (Coal) [Member] | Public Service Company of New Mexico [Member] | Unit 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Composite Interest	38.457%
Jointly owned utility plant, future proportionate ownership share	64.50%
SJGS (Coal) [Member] | PNMR Development [Member] | Unit 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, future proportionate ownership share	12.80%
Palo Verde Nuclear Generating Station [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 797,793
Accumulated Depreciation	(334,887)
Construction Work in Progress	$ 38,946
Composite Interest	10.20%
Period of time for the original full power operating licenses	40 years
Number of units (in generating units) | generating_unit	3
Operating lease, option term extensions	20 years
Four Corners [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Number of units (in generating units) | generating_unit	2
Four Corners Units 4 and 5 (Coal) [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 188,026
Accumulated Depreciation	(103,584)
Construction Work in Progress	$ 52,869
Composite Interest	13.00%
Luna (Gas) [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 69,678
Accumulated Depreciation	(25,386)
Construction Work in Progress	$ 259
Composite Interest	33.33%
San Juan Generating Station Units 2 and 3 [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 471,800	468,200
Accumulated Depreciation	(203,900)	(193,300)
Construction Work in Progress		2,200
Net book value	$ 267,900	277,100
San Juan Generating Station Units 2 and 3 [Member] | Public Service Company of New Mexico [Member] | Clean Air Act, SNCR [Member]
Jointly Owned Utility Plant Interests [Line Items]
Regulatory disallowance		$ 127,600
SJGS Units 1 and 2 [Member] | Public Service Company of New Mexico [Member]
Jointly Owned Utility Plant Interests [Line Items]
Composite Interest	50.00%