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Pension and Other Postretirement Benefits Components of Net Periodic Benefit Cost (Income) Recognized (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Public Service Company of New Mexico [Member] | Pension Plan [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | $ 0 | $ 0 | $ 0
Interest cost | 28,255 | 30,163 | 28,142
Expected return on plan assets | (39,323) | (38,044) | (41,930)
Amortization of net (gain) loss | 14,820 | 13,020 | 14,840
Amortization of prior service cost | (965) | (965) | 76
Net periodic benefit cost | 2,787 | 4,174 | 1,128
Public Service Company of New Mexico [Member] | Other Postretirement Benefits [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | 204 | 181 | 260
Interest cost | 4,089 | 4,630 | 4,113
Expected return on plan assets | (5,610) | (5,638) | (5,043)
Amortization of net (gain) loss | 1,966 | 2,225 | 4,242
Amortization of prior service cost | (642) | (1,343) | (1,343)
Net periodic benefit cost | 7 | 55 | 2,229
Public Service Company of New Mexico [Member] | Executive Retirement Program [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | 0 | 0 | 0
Interest cost | 760 | 822 | 720
Amortization of net (gain) loss | 325 | 210 | 232
Amortization of prior service cost | 0 | 0 | 0
Net periodic benefit cost | 1,085 | 1,032 | 952
Texas-New Mexico Power Company [Member] | Pension Plan [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | 0 | 0 | 0
Interest cost | 3,043 | 3,193 | 3,087
Expected return on plan assets | (4,420) | (4,526) | (4,849)
Amortization of net (gain) loss | 782 | 665 | 1,049
Amortization of prior service cost | 0 | 0 | 0
Net periodic benefit cost | (595) | (668) | (713)
Texas-New Mexico Power Company [Member] | Other Postretirement Benefits [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | 247 | 237 | 299
Interest cost | 608 | 619 | 566
Expected return on plan assets | (520) | (534) | (503)
Amortization of net (gain) loss | 0 | (122) | 0
Amortization of prior service cost | 0 | 32 | 57
Net periodic benefit cost | 335 | 232 | 419
Texas-New Mexico Power Company [Member] | Executive Retirement Program [Member] |  |  |
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] |  |  |
Service cost | 0 | 0 | 0
Interest cost | 36 | 39 | 36
Amortization of net (gain) loss | 5 | 0 | 0
Amortization of prior service cost | 0 | 0 | 0
Net periodic benefit cost | $ 41 | $ 39 | $ 36

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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 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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