Summary of Budgeted Construction Expenditures (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Summary of Budgeted Construction Expenditures [Line Items]
2012	$ 286.6
2013	266.0
2014	275.5
2015	255.8
2016	223.0
Total	1,306.9
Public Service Company of New Mexico [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2012	170.7
2013	168.5
2014	167.4
2015	153.2
2016	149.9
Total	809.7
Texas-New Mexico Power Company [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2012	95.2
2013	86.1
2014	95.7
2015	90.2
2016	61.0
Total	428.2
Other Subsidiaries [Member]
Summary of Budgeted Construction Expenditures [Line Items]
2012	20.7
2013	11.4
2014	12.4
2015	12.4
2016	12.1
Total	$ 69.0