FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Financial Instruments Measured at Fair Value on a Recurring Basis) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Assets
Cash Equivalent	$ 10	[1]	$ 0	[1]
Restricted Cash	2	[1]	2	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	25	[2]	22	[2]
Total Assets	38		26
Liabilities
Liabilities	(10)		(10)
Net Total Assets (Liability)	28		16
Energy Contracts [Member]
Liabilities
Derivative Liability	(5)		(2)
Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)		(1)
Interest Rate Swap [Member]
Liabilities
Derivative Liability	(4)		(7)
Energy Contracts [Member]
Assets
Derivative Assets	1	[3]	2	[3]
Level 1 [Member]
Assets
Cash Equivalent	10	[1]	0	[1]
Restricted Cash	2	[1]	2	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Total Assets	12		2
Liabilities
Liabilities	0		0
Net Total Assets (Liability)	12		2
Level 1 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 1 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Level 1 [Member] | Energy Contracts [Member]
Assets
Derivative Assets	0	[3]	0	[3]
Level 2 [Member]
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	25	[2]	22	[2]
Total Assets	26		23
Liabilities
Liabilities	(6)		(7)
Net Total Assets (Liability)	20		16
Level 2 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(2)	[3]	0	[3]
Level 2 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3]	0	[3]
Level 2 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(4)	[4]	(7)	[4]
Level 2 [Member] | Energy Contracts [Member]
Assets
Derivative Assets	1	[3]	1	[3]
Level 3 [Member]
Assets
Cash Equivalent	0	[1]	0	[1]
Restricted Cash	0	[1]	0	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2]	0	[2]
Derivative Assets	0		1
Total Assets	0		1
Liabilities
Derivative Liability	(4)		(3)
Liabilities	(4)		(3)
Net Total Assets (Liability)	(4)		(2)
Level 3 [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(3)	[3]	(2)	[3]
Level 3 [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(1)	[3]
Level 3 [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4]	0	[4]
Level 3 [Member] | Energy Contracts [Member]
Assets
Derivative Assets	0	[3]	1	[3]
Netting [Member]
Assets
Cash Equivalent	0	[1],[5]	0	[1],[5]
Restricted Cash	0	[1],[5]	0	[1],[5]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	0	[2],[5]	0	[2],[5]
Total Assets	(1)	[5]	(1)	[5]
Liabilities
Liabilities	1	[5]	1	[5]
Net Total Assets (Liability)	0	[5]	0	[5]
Netting [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	1	[3],[5]	1	[3],[5]
Netting [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	0	[3],[5]	0	[3],[5]
Netting [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	0	[4],[5]	0	[4],[5]
Netting [Member] | Energy Contracts [Member]
Assets
Derivative Assets	(1)	[3],[5]	(1)	[3],[5]
Net Fair Value [Member]
Assets
Cash Equivalent	10	[1]	0	[1]
Restricted Cash	2	[1]	2	[1]
Rabbi Trust Investments to Support the Deferred Compensation and SERP	25	[2]	22	[2]
Total Assets	37		25
Liabilities
Liabilities	(9)		(9)
Net Total Assets (Liability)	28		16
Net Fair Value [Member] | Energy Contracts [Member]
Liabilities
Derivative Liability	(4)	[3]	(1)	[3]
Net Fair Value [Member] | Energy Contracts Cash Flow Hedge [Member]
Liabilities
Derivative Liability	(1)	[3]	(1)	[3]
Net Fair Value [Member] | Interest Rate Swap [Member]
Liabilities
Derivative Liability	(4)	[4]	(7)	[4]
Net Fair Value [Member] | Energy Contracts [Member]
Assets
Derivative Assets	$ 0	[3]	$ 1	[3]

[1] Cash Equivalents and Restricted Cash represent amounts held in money market funds and certificates of deposit valued at cost, including interest, which approximates fair market value. Cash Equivalents are included in Cash and Cash Equivalents on the balance sheets. Restricted Cash is included in Investments and Other Property – Other on the balance sheets.

[2] Rabbi Trust Investments include amounts related to deferred compensation and Supplement Executive Retirement Plan (SERP) benefits held in mutual and money market funds valued at quoted prices traded in active markets. These investments are included in Investments and Other Property – Other on the balance sheets.

[3] Energy Contracts include gas swap agreements (Level 2), power options (Level 2), gas options (Level 3), and forward power purchase and sales contracts (Level 3) entered into to reduce exposure to energy price risk. These contracts are included in Derivative Instruments on the balance sheets. The valuation techniques are described below.

[4] Interest Rate Swaps still held are valued based on the 6-month London Interbank Offered Rate (LIBOR). An interest rate swap valued based on the Securities Industry and Financial Markets Association Municipal swap index matured in September 2014. These interest rate swaps are included in Derivative Instruments on the balance sheets.

[5] All energy contracts are subject to legally enforceable master netting arrangements to mitigate credit risk. We have presented the effect of offset by counterparty; however, we present derivatives on a gross basis on the balance sheets.