Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7

-Footnote 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3044-108585

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7, 26

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

+ Details

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References+ Details

Capitalization, Short-term Debt (Details) (USD $)	3 Months Ended
Capitalization, Short-term Debt (Details) (USD $)	Mar. 31, 2012 Extensions	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 Line of Credit [Member]	Dec. 31, 2011 Line of Credit [Member]	Mar. 31, 2012 PNM Resources [Member] Revolving credit facility [Member]	Dec. 31, 2011 PNM Resources [Member] Revolving credit facility [Member]	Mar. 31, 2012 PNM Resources [Member] Bi-lateral line of credit [Member]	Dec. 31, 2011 PNM Resources [Member] Bi-lateral line of credit [Member]	Mar. 31, 2012 Public Service Company of New Mexico [Member]	Dec. 31, 2011 Public Service Company of New Mexico [Member]	Mar. 31, 2011 Public Service Company of New Mexico [Member]	Dec. 31, 2010 Public Service Company of New Mexico [Member]	Mar. 31, 2012 Public Service Company of New Mexico [Member] Revolving credit facility [Member]	Dec. 31, 2011 Public Service Company of New Mexico [Member] Revolving credit facility [Member]	Mar. 31, 2012 Texas-New Mexico Power Company [Member]	Dec. 31, 2011 Texas-New Mexico Power Company [Member]	Mar. 31, 2011 Texas-New Mexico Power Company [Member]	Dec. 31, 2010 Texas-New Mexico Power Company [Member]	Mar. 31, 2012 Texas-New Mexico Power Company [Member] Revolving credit facility [Member]	Dec. 31, 2011 Texas-New Mexico Power Company [Member] Revolving credit facility [Member]	Apr. 27, 2012 Available Borrowing Capacity [Member]	Apr. 27, 2012 Available Borrowing Capacity [Member] PNM Resources [Member]	Apr. 27, 2012 Available Borrowing Capacity [Member] Public Service Company of New Mexico [Member]	Apr. 27, 2012 Available Borrowing Capacity [Member] Texas-New Mexico Power Company [Member]	Apr. 27, 2012 Affiliated Entity [Member] Intercompany loan agreements [Member] Texas-New Mexico Power Company [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Extension Option, Years	1 year
Short-term Debt, Weighted Average Interest Rate							2.00%								1.75%
Line of Credit Facility, Remaining Borrowing Capacity																							$ 587,800,000	$ 181,700,000	$ 331,400,000	$ 74,700,000
Cash and cash equivalents	6,976,000	15,091,000	12,940,000	15,404,000							300,000	12,307,000	55,000	10,336,000			4,700,000	1,000	494,000	1,000
Short-term debt – affiliate																	0	700,000									6,700,000
Line of Credit Facility, Maximum Borrowing Capacity							300,000,000		5,000,000						400,000,000						75,000,000
Line of Credit Facility, Number of Extension Options	2
Short-term debt	$ 149,800,000	$ 82,700,000			$ 149,800,000	$ 82,700,000	$ 105,700,000	$ 16,700,000	$ 0	$ 0	$ 44,100,000	$ 66,000,000			$ 44,100,000	$ 66,000,000					$ 0	$ 0