SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Thousands	Sep. 30, 2023	May 25, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 2,723,931		$ 2,176,080
Offshore Wind Business
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)	50.00%	50.00%
Investments in unconsolidated affiliates	$ 2,578,600		1,947,100
Natural Gas Pipeline - Algonquin Gas Transmission, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)	15.00%
Investments in unconsolidated affiliates	$ 116,800		118,800
Renewable Energy Investment Fund
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)	90.00%
Investments in unconsolidated affiliates	$ 0		84,100
Other
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 28,500		$ 26,100