v3.19.3.a.u2

Commitments and contingencies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2019
Management Service Commitments |
Schedule of estimated commitments under fuel supply and transportation agreements |
2020 |  | $ | 0.4 |
2021 |  |  | 0.4 |
2022 |  |  | 0.2 |
2023 |  |  | — |
2024 |  |  | — |
Thereafter |  |  | — |
|  | $ | 1.0 |
Fuel Supply and Transportation Commitments |
Schedule of estimated commitments under fuel supply and transportation agreements |
2020 |  | $ | 5.0 |
2021 |  |  | 5.0 |
2022 |  |  | 5.2 |
2023 |  |  | — |
2024 |  |  | — |
Thereafter |  |  | — |
|  | $ | 15.2 |

X
- Definition Tabular disclosure of key provisions of an arrangement under which the entity has agreed to purchase goods or services over a period of time greater than one year or the normal operating cycle, if longer, including the item for which expenditures will be made, minimum quantities, milestones, time period and committed amount. + References No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=at_MaintenanceServicesForTurbineEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=at_FuelAndTransportationServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |