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Pension and Other Postretirement Benefit Plans (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Public Service Company of New Mexico [Member] | Pension Plan [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | $ 0 | $ 0 | $ 0 | $ 0
Interest cost | 7,064,000 | 7,541,000 | 21,191,000 | 22,622,000
Expected return on plan assets | (9,831,000) | (9,511,000) | (29,492,000) | (28,533,000)
Amortization of net (gain) loss | 3,705,000 | 3,255,000 | 11,115,000 | 9,765,000
Amortization of prior service cost | (241,000) | (241,000) | (724,000) | (724,000)
Net Periodic Benefit Cost (Income) | 697,000 | 1,044,000 | 2,090,000 | 3,130,000
Contributions by employer | 0 | 0 | 30,000,000 | 0
Total expected employer contributions for fiscal year | 0 |  | 0 |
Estimated future employer contributions after current fiscal year | 22,000,000 |  | $ 22,000,000 |
Public Service Company of New Mexico [Member] | Pension Plan [Member] | Minimum [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate |  |  | 4.80% |
Public Service Company of New Mexico [Member] | Pension Plan [Member] | Maximum [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate |  |  | 5.50% |
Public Service Company of New Mexico [Member] | OPEB [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | 51,000 | 45,000 | $ 153,000 | 136,000
Interest cost | 1,022,000 | 1,159,000 | 3,067,000 | 3,473,000
Expected return on plan assets | (1,403,000) | (1,410,000) | (4,208,000) | (4,229,000)
Amortization of net (gain) loss | 491,000 | 556,000 | 1,474,000 | 1,669,000
Amortization of prior service cost | (160,000) | (336,000) | (481,000) | (1,008,000)
Net Periodic Benefit Cost (Income) | 1,000 | 14,000 | 5,000 | 41,000
Contributions by employer | 800,000 | 800,000 | 2,400,000 | 2,400,000
Total expected employer contributions for fiscal year | 3,500,000 |  | 3,500,000 |
Estimated future employer contributions after current fiscal year | 14,000,000 |  | 14,000,000 |
Public Service Company of New Mexico [Member] | Other Pension Plan [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 190,000 | 205,000 | 570,000 | 616,000
Expected return on plan assets | 0 | 0 | 0 | 0
Amortization of net (gain) loss | 81,000 | 52,000 | 243,000 | 157,000
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | 271,000 | 257,000 | 813,000 | 773,000
Contributions by employer | 400,000 | 400,000 | 1,200,000 | 1,200,000
Total expected employer contributions for fiscal year | 1,500,000 |  | 1,500,000 |
Texas-New Mexico Power Company [Member] | Pension Plan [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 761,000 | 798,000 | 2,282,000 | 2,395,000
Expected return on plan assets | (1,105,000) | (1,132,000) | (3,315,000) | (3,395,000)
Amortization of net (gain) loss | 195,000 | 166,000 | 586,000 | 499,000
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | (149,000) | (168,000) | (447,000) | (501,000)
Contributions by employer |  |  |  | 0
Estimated future employer contributions after current fiscal year | $ 0 |  | 0 |
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | Minimum [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate | 4.80% |  |  |
Texas-New Mexico Power Company [Member] | Pension Plan [Member] | Maximum [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Assumptions used calculating net periodic benefit cost, discount rate | 5.50% |  |  |
Texas-New Mexico Power Company [Member] | OPEB [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | $ 62,000 | 59,000 | 185,000 | 178,000
Interest cost | 152,000 | 155,000 | 456,000 | 464,000
Expected return on plan assets | (130,000) | (133,000) | (390,000) | (400,000)
Amortization of net (gain) loss | 0 | (31,000) | 0 | (92,000)
Amortization of prior service cost | 0 | 8,000 | 0 | 24,000
Net Periodic Benefit Cost (Income) | 84,000 | 58,000 | 251,000 | 174,000
Contributions by employer |  | 0 | 0 | 300,000
Total expected employer contributions for fiscal year | 300,000 |  | 300,000 |
Estimated future employer contributions after current fiscal year | 1,400,000 |  | 1,400,000 |
Texas-New Mexico Power Company [Member] | Other Pension Plan [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Service cost | 0 | 0 | 0 | 0
Interest cost | 9,000 | 10,000 | 27,000 | 29,000
Expected return on plan assets | 0 | 0 | 0 | 0
Amortization of net (gain) loss | 1,000 | 0 | 3,000 | 0
Amortization of prior service cost | 0 | 0 | 0 | 0
Net Periodic Benefit Cost (Income) | 10,000 | 10,000 | 30,000 | 29,000
Total expected employer contributions for fiscal year | 100,000 |  | 100,000 |
Texas-New Mexico Power Company [Member] | Other Pension Plan [Member] | Maximum [Member] |  |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |  |
Contributions by employer | $ 100,000 | $ 100,000 | $ 100,000 | $ 100,000

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- Definition Defined Benefit Plan Total Expected Employer Contributions for Fiscal Year + References No definition available. + Details
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- Definition The amount of gains or losses recognized in net periodic benefit cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(4) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Prior Service Cost -URI http://asc.fasb.org/extlink&oid=49177896 + Details
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- Definition The interest rate used to adjust for the time value of money. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512171 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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- Definition The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Service Cost (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6525008 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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