Schedule I - Condensed Financial Information Of Parent (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Cash and cash equivalents	$ 10	$ 9	$ 292	$ 5
Miscellaneous accounts and notes receivable	70	63
Other current assets	98	113
Total current assets	1,612	1,593
Accumulated deferred income taxes, net	6	7
Other assets	522	538
TOTAL ASSETS	25,945	24,699
LIABILITIES AND EQUITY
Short-term debt	484	558
Other current liabilities	326	274
Total current liabilities	2,940	2,674
Long-term Debt, Net	7,094	6,595
Pension and other postretirement benefits	545	769
Other deferred credits and liabilities	460	477
Commitments and Contingencies
Retained earnings	1,660	1,568
Accumulated other comprehensive loss	(18)	(23)
Total equity	7,326	7,245	7,088
TOTAL LIABILITIES AND EQUITY	25,945	24,699
Parent Company
ASSETS
Cash and cash equivalents	0	1	$ 0	$ 1
Advances to money pool	13	27
Accounts receivable - affiliates	46	31
Miscellaneous accounts and notes receivable	0	26
Other current assets	8	8
Total current assets	67	93
Investments in subsidiaries	7,944	7,498
Note receivable - affiliates	75	350
Accumulated deferred income taxes, net	222	419
Other assets	140	135
TOTAL ASSETS	8,448	8,495
LIABILITIES AND EQUITY
Short-term debt	383	507
Borrowings from money pool	28	33
Accounts payable – affiliates	6	13
Other current liabilities	27	17
Total current liabilities	444	570
Long-term Debt, Net	696	694
Pension and other postretirement benefits	37	45
Other deferred credits and liabilities	87	83
Total liabilities	1,264	1,392
Common stock, $.01 par value, 400.0 shares authorized – 242.6 shares outstanding	2	2
Other paid-in capital, principally premium on common stock	5,540	5,556
Retained earnings	1,660	1,568
Accumulated other comprehensive loss	(18)	(23)
Total equity	7,184	7,103
TOTAL LIABILITIES AND EQUITY	$ 8,448	$ 8,495