VARIABLE INTEREST ENTITIES - POWER PURCHASE AGREEMENT (Details) - Power purchase agreement $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) MW
Variable interest entities
Firm capacity from power purchase agreement (in megawatts) | MW	236
Minimum energy requirements over remaining term of power purchase agreement (in megawatts) | MW	0
Remaining term of power purchase agreement (in years)	1 year
Residual guarantee associated with power purchase agreement | $	$ 0.0
Required capacity payments over remaining term of power purchase agreement | $	$ 6.5