Schedule I - Condensed Financial Information Of Parent (Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
ASSETS
Cash and cash equivalents	$ 209	$ 255	$ 545	$ 622
Accounts and notes receivable - affiliates	401	473
Other current assets	95	112
Total current assets	2,369	2,295
Other non-current assets	749	845
TOTAL ASSETS	21,835	23,645	23,511
LIABILITIES AND EQUITY
Short-term debt		148
Other current liabilities	188	207
Total current liabilities	1,698	1,785
Long-term debt	6,626	6,677
Other deferred credits and liabilities	668	447
Commitments and Contingencies
Retained earnings	1,006	2,369
Accumulated other comprehensive income (loss)	(8)	(50)
Total equity	6,767	8,068	7,884
TOTAL LIABILITIES AND EQUITY	21,835	23,645
Parent Company [Member]
ASSETS
Cash and cash equivalents	23	3	4	24
Advances to money pool	316	340
Accounts and notes receivable - affiliates	31	57
Other current assets	49
Total current assets	419	400
Investments in subsidiaries	5,962	7,482
Note receivable - affiliates	462	425
Other non-current assets	320	333
TOTAL ASSETS	7,163	8,640
LIABILITIES AND EQUITY
Short-term debt		148
Accounts payable - affiliates	10	13
Other current liabilities	33	62
Total current liabilities	43	223
Long-term debt	424	424
Other deferred credits and liabilities	80	74
Total liabilities	547	721
Common stock, $.01 par value, 400.0 shares authorized – shares outstanding of 242.6	2	2
Other paid-in capital, principally premium on common stock	5,616	5,598
Retained earnings	1,006	2,369
Accumulated other comprehensive income (loss)	(8)	(50)
Total equity	6,616	7,919
TOTAL LIABILITIES AND EQUITY	$ 7,163	$ 8,640