Financing Schedule of Short-term Debt (Details) (USD $)	Dec. 31, 2011	Oct. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Public Service Company of New Mexico [Member]	Oct. 31, 2011 Public Service Company of New Mexico [Member]	Dec. 31, 2010 Public Service Company of New Mexico [Member]	Dec. 31, 2011 Texas-New Mexico Power Company [Member]	Dec. 31, 2010 Texas-New Mexico Power Company [Member]	Apr. 30, 2009 Texas-New Mexico Power Company [Member]	Jan. 02, 2009 Texas-New Mexico Power Company [Member]	Dec. 31, 2011 PNMR [Member]	Dec. 31, 2010 PNMR [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount	$ 11,100,000			$ 4,700,000			$ 300,000
Line of Credit Facility, Maximum Borrowing Capacity		300,000,000			400,000,000		75,000,000		75,000,000	200,000,000
Securities Received as Collateral									75,000,000
Line of Credit Facility, Amount Outstanding				66,000,000		190,000,000	0	0			16,700,000	32,000,000
Line Of Credit Facility Amount Outstanding, Local Institutions	5,000,000										0	0
Short-term debt	82,700,000		222,000,000	66,000,000		190,000,000
Line of Credit Facility Original Maximum Borrowing Capacity	600,000,000			400,000,000
Line of Credit Facility Reduction of Borrowing Capacity	517,000,000			368,000,000
Short-term Debt, Weighted Average Interest Rate	2.05%			1.80%
Line of Credit Facility and Local Lines of Credit Remaining Borrowing Capacity	266,200,000
Line of Credit Facility, Remaining Borrowing Capacity	584,900,000			244,000,000			74,700,000
Invested Cash and Cash Equivalents	$ 600,000			$ 0			$ 0