| Cover | Mar. 31, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 31, 2021 |
| Entity File Number | 001-34691 |
| Entity Registrant Name | ATLANTIC POWER CORPORATION |
| Entity Central Index Key | 0001419242 |
| Entity Tax Identification Number | 55-0886410 |
| Entity Incorporation, State or Country Code | A1 |
| Entity Address, Address Line One | 3 Allied Drive |
| Entity Address, Address Line Two | Suite 155 |
| Entity Address, City or Town | Dedham |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02026 |
| City Area Code | 617 |
| Local Phone Number | 977-2400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Shares, no par value, and the associated Rights to Purchase Common Shares |
| Trading Symbol | AT |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
