SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Investments in Unconsolidated Affliates (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 1,719,878	$ 1,436,293
Offshore Wind Business - North East Offshore
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Investments in unconsolidated affiliates	$ 1,487,100	1,213,600
Natural Gas Pipeline - Algonquin Gas Transmission, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest	15.00%
Investments in unconsolidated affiliates	$ 119,300	121,900
Renewable Energy Investment Fund
Schedule of Equity Method Investments [Line Items]
Ownership interest	90.00%
Investments in unconsolidated affiliates	$ 88,400	76,500
Other
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	$ 25,100	$ 24,300