Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
ASSETS
Cash and cash equivalents	$ 66	$ 37	$ 67	$ 48
Restricted cash	21	23
Accounts receivable	1,250	1,276
Property, plant, and equipment, net	18,550	18,034
Total Assets	29,462	28,662
LIABILITIES
Current portion long-term debt, including capital leases	15	473
Mortgage bonds, notes, and other	8,691	8,265
Variable Interest Entity, Primary Beneficiary
ASSETS
Cash and cash equivalents	26	14
Restricted cash	6	8
Accounts receivable	22	18
Inventories	115	82
Property, plant, and equipment, net	70	66
Other current and long-term assets	1	4
Total Assets	240	192
LIABILITIES
Accounts payable and accrued current liabilities	24	13
Current portion long-term debt, including capital leases	6	8
Mortgage bonds, notes, and other	5	10
Other current and long-term liabilities	16	6
Total Liabilities	$ 51	$ 37