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Lease Commitments - Narrative (Details) $ in Millions |  | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jan. 15, 2016 USD ($) lease MW | Dec. 31, 2017 USD ($) lease lessor | Apr. 01, 2015 USD ($) | Jan. 15, 2015 lease | Dec. 31, 1986 lease | Dec. 31, 1985 lease
Lease commitments |  |  |  |  |  |
Operating lease, option term extensions |  | 2 years |  |  |  |
Operating leases, renewal options after original lease term |  | 6 years |  |  |  |
Operating leases, period to notify of lease retention |  | 3 years |  |  |  |
Public Service Company of New Mexico | TGP Granada, LLC and its affiliate Complaint |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Lease ownership in EIP |  | 60.00% |  |  |  |
Additional area leased of the EIP |  |  | 40.00% |  |  |
Option to purchase leased capacity at fair value |  |  | $ 7.7 |  |  |
Public Service Company of New Mexico | Navajo Nation |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of operating leases set to expire | lease |  | 0 |  |  |  |
Operating leases, period to expiration of the lease |  | 5 years |  |  |  |
Annual lease payments |  | $ 6.0 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of leases | lease |  |  |  |  | 4 | 4
Rental payments, fixed renewal option period during original terms of leases |  | 50.00% |  |  |  |
Lease covenants, restrictions on conveying, transferring, leasing, and dividends (more than) |  | 5.00% |  |  |  |
Loss contingency, range of possible loss, portion not accrued (up to) |  | $ 169.9 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 1 Leases |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Annual lease payments |  | 33.0 |  |  |  |
Number of leases | lease |  |  |  | 4 |  | 4
Annual lease payments during renewal period |  | 16.5 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 2 Leases |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Annual lease payments |  | $ 23.7 |  |  |  |
Number of leases | lease | 1 | 3 |  |  | 4 |
Annual lease payments during renewal period |  | $ 1.6 |  |  |  |
Estimated purchase price of leased asset | $ 78.1 |  |  |  |  |
Leased capacity to be purchased (in megawatts) | MW | 31.25 |  |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 1, Lease with Maximum Option Period Provision |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of lessors | lessor |  | 4 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 2, Lease with Maximum Option Period Provision |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of leases | lease |  | 1 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 1, Lease Expires in 2023 |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of leases | lease |  | 4 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 2, Lease Expires in 2024 |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of leases | lease |  | 1 |  |  |  |
Public Service Company of New Mexico | Palo Verde Nuclear Generating Station, Unit 2 Leases 32.76 MW |  |  |  |  |  |
Lease commitments |  |  |  |  |  |
Number of leases | lease | 2 |  |  |  |  |
Estimated purchase price of leased asset | $ 85.2 |  |  |  |  |
Additional capacity to be leased (in megawatts) | MW | 32.76 |  |  |  |  |

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