Acquisitions and Dispositions (Details) (USD $)	12 Months Ended			0 Months Ended	3 Months Ended	12 Months Ended		12 Months Ended		0 Months Ended	1 Months Ended		12 Months Ended		1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Sep. 23, 2011 First Choice [Member]	Dec. 31, 2011 First Choice [Member]	Dec. 31, 2011 First Choice [Member]	Oct. 31, 2011 First Choice [Member]	Dec. 31, 2009 PNM Gas [Member]	Dec. 31, 2009 Public Service Company of New Mexico [Member]	Jan. 30, 2009 Public Service Company of New Mexico [Member] PNM Gas [Member]	Jul. 31, 2008 Public Service Company of New Mexico [Member] PNM Gas [Member]	Jan. 31, 2008 Public Service Company of New Mexico [Member] PNM Gas [Member]	Dec. 31, 2009 Public Service Company of New Mexico [Member] PNM Gas [Member]	Dec. 31, 2009 PNMR [Member] PNM Gas [Member]	Jun. 30, 2007 Palo Verde Nuclear Generating Station [Member] Public Service Company of New Mexico [Member] mw	Dec. 31, 2008 Palo Verde Nuclear Generating Station [Member] Public Service Company of New Mexico [Member]
Significant Acquisitions and Disposals [Line Items]
Sale of business segment subject to adjustments of certain componets of working capital				$ 270,000,000
Amount received including estimate of components of working capital				329,300,000
Gain on sale of business segment	174,925,000	0	0		174,900,000	174,900,000
Working capital that purchaser disputing is overstated							4,200,000
Working capital that parent is disputing is understated							(6,500,000)
Cash from sale of PNM Gas segment												620,000,000
Gain on contract termination								292,000						15,000,000
Gain on sale of PNM Gas segment								98,425,000		65,300,000
Income taxes on sale of PNM Gas segment										33,100,000
Amount received related to working capital true-ups										32,900,000
Disposal Group Cash Received from Contract Termination											15,000,000
After-tax gain on termination of CRHC agreement														9,100,000
After-tax charge to AOCI for retirement programs transferred to NMGC													64,800,000
PNM expense related to contingent liabilities									5,400,000				5,400,000
Dividend payment to PNMR													220,000,000
Repayments of debt													15,000,000
Ownership percentage of PNMR's subsidiary in purchased trust															100.00%
Undivided interest in PVNGS Unit 2															2.27%
Mega Watts															29.8
Purchase price, cash paid																39,100,000
Liabilities incurred																$ 32,000,000