RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Notional Principal or Quantity Information (Details) - Sep. 30, 2021 € in Millions, ¥ in Millions, £ in Millions, $ in Millions, $ in Millions	USD ($) MWh MMBbls Bcf	GBP (£) MWh MMBbls Bcf	EUR (€) MWh MMBbls Bcf	JPY (¥) MWh MMBbls Bcf	CAD ($) MWh MMBbls Bcf
Foreign exchange contracts - forwards - purchase | United States dollar
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021	$ 1,357
2022	1,750
2023	0
2024	0
2025	0
Thereafter	0
Derivative Notional Amount Outstanding	3,107
Foreign exchange contracts - forwards - purchase | Japanese yen
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 | ¥				¥ 0
2022 | ¥				72,500
2023 | ¥				0
2024 | ¥				0
2025 | ¥				0
Thereafter | ¥				0
Derivative Notional Amount Outstanding | ¥				¥ 72,500
Foreign exchange contracts - forwards - sell | United States dollar
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021	2,210
2022	6,354
2023	3,784
2024	2,480
2025	1,290
Thereafter	672
Derivative Notional Amount Outstanding	$ 16,790
Foreign exchange contracts - forwards - sell | GBP
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 | £		£ 62
2022 | £		28
2023 | £		29
2024 | £		30
2025 | £		30
Thereafter | £		60
Derivative Notional Amount Outstanding | £		£ 239
Foreign exchange contracts - forwards - sell | Euro
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 | €			€ 38
2022 | €			94
2023 | €			92
2024 | €			91
2025 | €			86
Thereafter | €			428
Derivative Notional Amount Outstanding | €			€ 829
Interest rate contracts - short-term borrowings
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021					$ 992
2022					395
2023					47
2024					35
2025					30
Thereafter					90
Derivative Notional Amount Outstanding					1,589
Interest rate contracts - long-term debt pay fixed rate
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021					0
2022					1,987
2023					1,333
2024					0
2025					0
Thereafter					0
Derivative Notional Amount Outstanding					3,320
Equity contracts
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021					40
2022					19
2023					26
2024					20
2025					0
Thereafter					0
Derivative Notional Amount Outstanding					$ 105
Commodity contracts | Natural gas
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 (bcf / mmbbls) | Bcf	19	19	19	19	19
2022 (bcf / mmbbls) | Bcf	55	55	55	55	55
2023 (bcf / mmbbls) | Bcf	15	15	15	15	15
2024 (bcf / mmbbls) | Bcf	4	4	4	4	4
2025 (bcf / mmbbls) | Bcf	10	10	10	10	10
Thereafter (bcf / mmbbls) | Bcf	(16)	(16)	(16)	(16)	(16)
Derivative Nonmonetary Notional Amount Outstanding | Bcf	87	87	87	87	87
Commodity contracts | Crude
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 (bcf / mmbbls) | MMBbls	12	12	12	12	12
2022 (bcf / mmbbls) | MMBbls	2	2	2	2	2
2023 (bcf / mmbbls) | MMBbls	0	0	0	0	0
2024 (bcf / mmbbls) | MMBbls	0	0	0	0	0
2025 (bcf / mmbbls) | MMBbls	0	0	0	0	0
Thereafter (bcf / mmbbls) | MMBbls	0	0	0	0	0
Derivative Nonmonetary Notional Amount Outstanding | MMBbls	14	14	14	14	14
Net purchase | Commodity contracts | Power
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2021 (MWH) | MWh	(18)	(18)	(18)	(18)	(18)
Net sell | Commodity contracts | Power
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2022 (MWH) | MWh	(43)	(43)	(43)	(43)	(43)
2023 (MWH) | MWh	(43)	(43)	(43)	(43)	(43)
2024 (MWH) | MWh	(43)	(43)	(43)	(43)	(43)
2025 (MWH) | MWh	(43)	(43)	(43)	(43)	(43)
Thereafter (MWH) | MWh	0	0	0	0	0
Total (MWH) | MWh	(42)	(42)	(42)	(42)	(42)