Construction Program and Jointly-Owned Electric Generating Plants - Summary of Budgeted Construction Expenditures (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Summary of Budgeted Construction Expenditures [Line Items]
2016	$ 546.8
2017	415.1
2018	397.7
2019	352.4
2020	325.0
Total	2,037.0
Public Service Company of New Mexico [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2016	396.4
2017	295.1
2018	269.3
2019	220.3
2020	183.7
Total	1,364.8
Public Service Company of New Mexico [Member] | San Juan Generating Station [Member]
Summary of Budgeted Construction Expenditures [Line Items]
Expenditures related to environmental upgrades	1.3
Budgeted construction expenditures related to replacement capacity	100.8
Public Service Company of New Mexico [Member] | Four Corners Units 4 and 5 (Coal) [Member]
Summary of Budgeted Construction Expenditures [Line Items]
Expenditures related to environmental upgrades	88.7
Public Service Company of New Mexico [Member] | Palo Verde Nuclear Generating Station, Unit 2 Leases [Member]
Summary of Budgeted Construction Expenditures [Line Items]
Budgeted Expenditures Related to purchase of assets currently leased	163.3
Texas-New Mexico Power Company [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2016	114.6
2017	101.1
2018	114.3
2019	117.0
2020	126.3
Total	573.3
Other Subsidiaries [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2016	35.8
2017	18.9
2018	14.1
2019	15.1
2020	15.0
Total	$ 98.9