Financing, Short-term Debt (Details) (USD $)	3 Months Ended																										1 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Line of Credit [Member]	Dec. 31, 2012 Line of Credit [Member]	Jun. 30, 2013 PNM Resources [Member] Revolving credit facility [Member]	Dec. 31, 2012 PNM Resources [Member] Revolving credit facility [Member]	Mar. 31, 2013 Public Service Company of New Mexico [Member]	Dec. 31, 2012 Public Service Company of New Mexico [Member]	Jun. 30, 2013 Public Service Company of New Mexico [Member] Revolving credit facility [Member]	Dec. 31, 2012 Public Service Company of New Mexico [Member] Revolving credit facility [Member]	Jun. 30, 2013 Texas-New Mexico Power Company [Member]	Mar. 31, 2013 Texas-New Mexico Power Company [Member]	Dec. 31, 2012 Texas-New Mexico Power Company [Member]	Jun. 30, 2013 Texas-New Mexico Power Company [Member] Revolving credit facility [Member]	Dec. 31, 2012 Texas-New Mexico Power Company [Member] Revolving credit facility [Member]	Jul. 26, 2013 Available Borrowing Capacity [Member]	Jul. 26, 2013 Available Borrowing Capacity [Member] PNM Resources [Member]	Jul. 26, 2013 Available Borrowing Capacity [Member] Public Service Company of New Mexico [Member]	Jul. 26, 2013 Available Borrowing Capacity [Member] Texas-New Mexico Power Company [Member]	Jul. 26, 2013 Subsequent Event [Member] PNM Resources [Member]	Jul. 26, 2013 Subsequent Event [Member] Public Service Company of New Mexico [Member]	Jul. 26, 2013 Subsequent Event [Member] Texas-New Mexico Power Company [Member]	Jul. 26, 2013 Affiliated Entity [Member] Intercompany loan agreements [Member] Texas-New Mexico Power Company [Member]	Jun. 30, 2013 PNMR Term Loan Agreement [Member]	Dec. 31, 2012 PNMR Term Loan Agreement [Member]	Dec. 31, 2012 PNMR Term Loan Agreement [Member] Notes Payable to Banks [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 300,000,000				$ 400,000,000					$ 75,000,000
Line of Credit Facility, Extension Option, Years	1 year
Proceeds from Short-term Debt																											100,000,000
Short-term Debt, Weighted Average Interest Rate		1.70%										1.82%													1.33%
Short-term debt	160,000,000		158,700,000	160,000,000	158,700,000	35,000,000	37,600,000	0	21,100,000	0	21,100,000		25,000,000	0	25,000,000	0									100,000,000	100,000,000
Line of Credit Facility, Remaining Borrowing Capacity																	710,900,000	261,400,000	396,800,000	52,700,000
Short-term debt – affiliate													35,800,000	28,300,000										37,800,000
Restricted Cash and Investments																					$ 3,100,000	$ 6,700,000	$ 0