Schedule I - Condensed Financial Information Of Parent (Balance Sheet) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Cash and Cash Equivalents, at Carrying Value	$ 16	$ 10
Miscellaneous accounts and notes receivable	79	70
Other current assets	63	98
Total current assets	1,533	1,612
Accumulated deferred income taxes, net	9	6
Other assets	650	522
TOTAL ASSETS	27,215	25,945
LIABILITIES AND EQUITY
Short-term debt	597	484
Other current liabilities	282	326
Total current liabilities	2,687	2,940
Long-term Debt, Net	7,859	7,094
Pension and other postretirement benefits	558	545
Other deferred credits and liabilities	408	460
Commitments and Contingencies
Retained earnings	2,024	1,660
Accumulated other comprehensive loss	(22)	(18)
Total equity	7,773	7,326	$ 7,245
TOTAL LIABILITIES AND EQUITY	$ 27,215	$ 25,945
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common Stock, Shares, Outstanding	244,500,000	242,600,000	242,600,000	242,600,000
Parent Company
ASSETS
Cash and Cash Equivalents, at Carrying Value	$ 0	$ 0
Advances to money pool	76	13
Accounts Receivable, Related Parties, Current	43	46
Other current assets	4	8
Total current assets	123	67
Investments in subsidiaries	8,559	7,944
Note receivable - affiliates	75	75
Accumulated deferred income taxes, net	108	222
Other assets	126	140
TOTAL ASSETS	8,991	8,448
LIABILITIES AND EQUITY
Short-term debt	470	383
Borrowings from money pool	46	28
Accounts payable – affiliates	10	6
Other current liabilities	12	27
Total current liabilities	538	444
Long-term Debt, Net	697	696
Pension and other postretirement benefits	43	37
Other deferred credits and liabilities	82	87
Total liabilities	1,360	1,264
Common stock, $.01 par value, 400.0 shares authorized – shares outstanding of 244.5 and 242.6, respectively	2	2
Other paid-in capital, principally premium on common stock	5,627	5,540
Retained earnings	2,024	1,660
Accumulated other comprehensive loss	(22)	(18)
Total equity	7,631	7,184
TOTAL LIABILITIES AND EQUITY	$ 8,991	$ 8,448
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common Stock, Shares, Outstanding	244,500,000	242,600,000