v3.19.3.a.u2

Summary of significant accounting policies - through derivatives (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 USD ($) item | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Accounts receivable |  |  |
Allowance for doubtful accounts | $ 0.0 | $ 0.0 |
Deferred financing costs |  |  |
Net carrying amount of deferred financing cost | 8.5 | 11.8 |
Amortization expense | $ 3.2 | $ 5.1 | $ 6.3
Impairment of long-lived assets, non-amortizing intangible assets and equity method investments |  |  |
Period prior to expiration of PPA when impairment review is conducted | 6 months |  |
Derivative financial instruments |  |  |
Number of interest rate swaps designated as cash flow hedges | item | 1 |  |
Minimum |  |  |
Deferred financing costs |  |  |
Amortization period | 1 year |  |
Investments accounted for by the equity method |  |  |
Ownership level triggering equity method of accounting, as a percent | 5.00% |  |
Maximum |  |  |
Deferred financing costs |  |  |
Amortization period | 6 years |  |
Investments accounted for by the equity method |  |  |
Ownership level triggering equity method of accounting, as a percent | 50.00% |  |
Impairment of long-lived assets, non-amortizing intangible assets and equity method investments |  |  |
Maximum percentage of ownership in entities in which consolidation is not required | 50.00% |  |

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- Definition Period of time prior to the expiration of an existing power purchase agreement at which an impairment review of the project is conducted. Expressed in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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