NOTES PAYABLE, LONG-TERM DEBT AND AVAILABLE CREDIT FACILITIES (Schedule of Committed and Available Credit Facilities) (Details) - USD ($) $ in Millions	May 31, 2016	Dec. 31, 2017
Revolving Credit Facility [Member] | Five Year Competitive Advance and Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		$ 5,000
Credit Available		5,000
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		100
Credit Available		100
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		100
Credit Available		100
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		280
Credit Available		280
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		100
Credit Available		100
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		100
Credit Available		100
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		200
Credit Available		200
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		200
Credit Available		200
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		200
Credit Available		200
Revolving Credit Facility [Member] | Bilateral Revolving Credit Facility
Line of Credit Facility [Line Items]
Committed Credit		100
Credit Available		100
Term Loan Facility [Domain] | DCC Term Loan Facility
Line of Credit Facility [Line Items]
Committed Credit		4,500
Credit Available		$ 0
Proceeds from credit facility	$ 4,500