Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
ASSETS
Cash and cash equivalents	$ 32	$ 37	$ 230	$ 48
Restricted cash	22	23
Accounts receivable	1,180	1,276
Property, plant, and equipment, net	18,295	18,034
Total Assets	28,769	28,662
LIABILITIES
Current portion long-term debt, including capital leases	165	473
Mortgage bonds, notes, and other	8,551	8,265
Variable Interest Entity, Primary Beneficiary
ASSETS
Cash and cash equivalents	11	14
Restricted cash	6	8
Accounts receivable	29	18
Inventories	101	82
Property, plant, and equipment, net	59	66
Other current and long-term assets	2	4
Total Assets	208	192
LIABILITIES
Accounts payable and accrued current liabilities	21	13
Current portion long-term debt, including capital leases	6	8
Mortgage bonds, notes, and other	7	10
Other current and long-term liabilities	6	6
Total Liabilities	$ 40	$ 37