Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim consolidated financial statements have been prepared in accordance with the SEC’s regulations for interim financial information and with the instructions to Form 10-Q. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The following notes should be read in conjunction with the accounting policies and other disclosures as set forth in the notes to the consolidated financial statements included in the Company’s 2021 Form 10-K. Interim results are not necessarily indicative of results for a full year. In the opinion of management, the accompanying unaudited interim consolidated financial statements contain all material adjustments consisting of normal and recurring accruals necessary to present fairly the Company’s consolidated financial position as of June 30, 2022, and results of operations, comprehensive income and cash flows for the three and six months ended June 30, 2022 and 2021.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions. These estimates and assumptions impact the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the consolidated financial statements. They also impact the reported amounts of net earnings during the reporting periods. Actual results could be different from these estimates.
Revenue Recognition and Contract Amortization	Revenue Recognition Revenue from Contracts with Customers The Company applies the guidance in ASC 606, Revenue from Contracts with Customers, or Topic 606, when recognizing revenue associated with its contracts with customers. The Company’s policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Power Purchase Agreements, or PPAs The majority of the Company’s revenues are obtained through PPAs or similar contractual agreements. Energy, capacity and where applicable, renewable attributes, from the majority of the Company’s renewable energy assets and certain conventional energy plants is sold through long-term PPAs and tolling agreements to a single counterparty, which is often a utility or commercial customer. The majority of these PPAs are accounted for as operating leases as the Company retained its historical lease assessments and classification upon adoption of ASC 842, Leases. ASC 842 requires the minimum lease payments received to be amortized over the term of the lease and contingent rentals are recorded when the achievement of the contingency becomes probable. Judgment is required by management in determining the economic life of each generating facility, in evaluating whether certain lease provisions constitute minimum payments or represent contingent rent and other factors in determining whether a contract contains a lease and whether the lease is an operating lease or capital lease. Certain of these leases have no minimum lease payments and all of the rental income under these leases is recorded as contingent rent on an actual basis when the electricity is delivered. Renewable Energy Credits, or RECs Renewable energy credits, or RECs, are usually sold through long-term PPAs or through REC contracts with counterparties. Revenue from the sale of self-generated RECs is recognized when the related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Thermal Revenues Steam and chilled water revenue is recognized as the Company transfers the product to the customer, based on customer usage as determined by meter readings taken at month-end. Some locations read customer meters throughout the month and recognize estimated revenue for the period between meter read date and month-end. For thermal contracts, the Company’s performance obligation to deliver steam and chilled water is satisfied over time and revenue is recognized based on the invoiced amount. The Thermal Business subsidiaries collect, and remit state and local taxes associated with sales to their customers, as required by governmental authorities. These taxes are presented on a net basis in the consolidated statements of income. As contracts for steam and chilled water are long-term contracts, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the Company cannot accurately estimate the amount of its unsatisfied performance obligations as it will vary based on customer usage, which will depend on factors such as weather and customer activity. On May 1, 2022, the Company completed the sale of 100% of its interests in the Thermal Business to KKR. For further details of the Thermal Disposition, refer to Note 3, Acquisitions and Dispositions. Contract Amortization Assets and liabilities recognized from power sales agreements assumed through acquisitions relating to the sale of electric capacity and energy in future periods arising from differences in contract and market prices are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes or on a straight-line basis, where applicable.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments provide for optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. These amendments apply only to contracts that reference LIBOR or another reference rate expected to be discontinued because of reference rate reform, which affects certain of the Company’s debt and interest rate swap agreements. The guidance is effective for all entities as of March 12, 2020 through December 31, 2022. As of June 30, 2022, the Company has applied the amendments to all of its eligible contract modifications, where applicable, during the reference rate reform period. Additionally, the Company has not elected any optional expedients provided in the standard.