NOTES PAYABLE, LONG-TERM DEBT AND AVAILABLE CREDIT FACILITIES NOTES PAYABLE, LONG-TERM DEBT AND AVAILABLE CREDIT FACILITIES (Schedule of Committed and Available Credit Facilities) (Details) $ in Millions	Sep. 30, 2015 USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 6,280
Line of Credit Facility, Remaining Borrowing Capacity	5,980
Five Year Competitive Advance and Revolving Credit Facility Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5,000	[1]
Line of Credit Facility, Remaining Borrowing Capacity	5,000	[1]
$100M Revolving Credit Facility Due 3/2016 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit Facility, Remaining Borrowing Capacity	100
Term Loan Facility [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	300
Line of Credit Facility, Remaining Borrowing Capacity	0
$100M Revolving Credit Facility Due 3/2020 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit Facility, Remaining Borrowing Capacity	100
$280M Revolving Credit Facility Due 3/2020 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	280
Line of Credit Facility, Remaining Borrowing Capacity	280
$100M Revolving Credit Facility Due 3/2020 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit Facility, Remaining Borrowing Capacity	100
$100M Revolving Credit Facility Due 3/2020 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit Facility, Remaining Borrowing Capacity	100
$200M Revolving Credit Facility due 3/2020 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	200
Line of Credit Facility, Remaining Borrowing Capacity	200
$100M Revolving Credit Facility Due 8/2016 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit Facility, Remaining Borrowing Capacity	$ 100

[1] The prior credit facility was terminated and replaced with a new credit facility, with substantially similar terms and conditions, on March 24, 2015.