RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Notional Principal or Quantity Information (Details) - Mar. 31, 2019 € in Millions, ¥ in Millions, £ in Millions, MMBbls in Millions, $ in Millions, $ in Millions, Bcf in Billions	USD ($) MWh Bcf MMBbls	CAD ($) MWh Bcf MMBbls	GBP (£) MWh Bcf MMBbls	EUR (€) MWh Bcf MMBbls	JPY (¥) MWh Bcf MMBbls
Euro
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2020 | €				€ 23
2021 | €				94
Foreign exchange contracts - forwards - purchase | United States dollar
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019	$ 895
2020	1
Foreign exchange contracts - forwards - purchase | Euro
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | €				168
Foreign exchange contracts - forwards - purchase | Japanese yen
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | ¥					¥ 32,662
2022 | ¥					¥ 20,000
Foreign exchange contracts - forwards - sell | United States dollar
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019	3,839
2020	4,893
2021	3,608
2022	1,944
2023	1,804
Thereafter	$ 1,856
Foreign exchange contracts - forwards - sell | GBP
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | £			£ 86
2020 | £			25
2021 | £			27
2022 | £			28
2023 | £			29
Thereafter | £			£ 120
Foreign exchange contracts - forwards - sell | Euro
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2022 | €				94
2023 | €				92
Thereafter | €				€ 606
Interest rate contracts - short-term borrowings
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019		$ 6,629
2020		6,178
2021		4,142
2022		407
2023		48
Thereafter		156
Interest rate contracts - long-term receive fixed rate
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019		0
2020		0
2021		0
2022		0
2023		0
Interest rate contracts - long-term debt pay fixed rate
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019		2,537
2020		3,142
2021		1,584
Equity contracts
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019		32
2020		$ 20
Commodity contracts | Natural gas
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | Bcf	(75)	(75)	(75)	(75)	(75)
2020 | Bcf	(15)	(15)	(15)	(15)	(15)
2022 | Bcf	(84)	(84)	(84)	(84)	(84)
2023 | Bcf	1	1	1	1	1
Commodity contracts | Crude oil
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | MMBbls	4	4	4	4	4
2020 | MMBbls	(2)	(2)	(2)	(2)	(2)
Commodity contracts | NGL
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | MMBbls	1	1	1	1	1
Commodity contracts | Power
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS
2019 | MWh	98	98	98	98	98
2020 | MWh	80	80	80	80	80
2021 | MWh	(3)	(3)	(3)	(3)	(3)
2022 | MWh	(43)	(43)	(43)	(43)	(43)
2023 | MWh	(43)	(43)	(43)	(43)	(43)
Thereafter | MWh	(43)	(43)	(43)	(43)	(43)