DEBT (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Line of Credit Facility [Line Items]
Proceeds from (Repayments of) Lines of Credit	$ 405,000,000	$ 155,000,000
Proceeds from Issuance of Commercial Paper	1,500,000,000
Line of Credit Facility, Current Borrowing Capacity	2,600,000,000
Line of Credit Facility, Remaining Borrowing Capacity	645,500,000
Repayments Of Commercial Paper Gross	12,293,400,000
Midcoast Energy Partners [Member]
Line of Credit Facility [Line Items]
Proceeds from (Repayments of) Lines of Credit	50,000,000
Proceeds from Lines of Credit	1,585,000,000
Repayments of Lines of Credit	1,635,000,000
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Proceeds from (Repayments of) Lines of Credit	136,400,000
Commercial paper aggregate principal amount supported by Credit Facilities	1,500,000,000
Fixed Rate Debt Obligations [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Fair Value Disclosure	6,000,000,000		$ 5,900,000,000
Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,975,000,000
Line of Credit Facility, Expiration Date	Sep. 26, 2020
Proceeds from Issuance of Commercial Paper	$ 3,071,700,000
Repayments of Commercial Paper	3,208,100,000
Credit Facility [Member] | Portion of Credit Facility Due in 2018 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 175,000,000
Line of Credit Facility, Expiration Date	Sep. 26, 2018
364-Day Credit Facility [Member]
Line of Credit Facility [Line Items]
Proceeds from (Repayments of) Lines of Credit	$ 455,000,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 625,000,000
Line of Credit Facility, Expiration Date	Jul. 01, 2016
Proceeds from Lines of Credit	$ 2,995,000,000
Repayments of Lines of Credit	$ 2,540,000,000
Debt Instrument, Term	364 days
Line of Credit Facility, Current Borrowing Capacity	$ 2,600,000,000
Standby Letters of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 175,000,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	Sep. 30, 2018
Revolving Credit Facility [Member] | Midcoast Energy Partners [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 810,000,000
Debt Instrument Number Of Requests For Extensions	4
Revolving Credit Facility [Member] | Portion Of Credit Facility Maturing In 2016 [Member] | Midcoast Energy Partners [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 140,000,000
Line of Credit Facility, Expiration Date	Nov. 13, 2016
Revolving Credit Facility [Member] | Portion of Facility Maturing in 2017 [Member] | Midcoast Energy Partners [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	Sep. 30, 2017
Revolving Credit Facility [Member] | Portion Of Credit Facility Maturing In 2017 [Member] | Midcoast Energy Partners [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 25,000,000