Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 63	$ 92	$ 66	$ 37
Restricted cash	23	21
Accounts receivable	1,395	1,522
Property, plant, and equipment, net	20,307	19,730
Goodwill	2,293	2,286
Intangible assets	883	842
Total Assets	33,071	32,041
LIABILITIES
Current portion long-term debt, including capital leases	109	14
Mortgage bonds, notes, and other	11,038	10,506
Variable interest entity, primary beneficiary, restricted
ASSETS
Cash and cash equivalents	44	63
Restricted cash	8	7
Accounts receivable	41	42
Inventories	87	115
Property, plant, and equipment, net	467	474
Goodwill	25	17
Intangible assets	576	586
Other current and long-term assets	1	2
Total Assets	1,249	1,306
LIABILITIES
Accounts payable and accrued current liabilities	55	51
Current portion long-term debt, including capital leases	3	5
Mortgage bonds, notes, and other	2	5
Other current and long-term liabilities	16	17
Total liabilities	76	78
SGG
ASSETS
Cash and cash equivalents	31	36
Restricted cash	0	0
Accounts receivable	11	8
Inventories	3	3
Property, plant, and equipment, net	397	398
Goodwill	25	17
Intangible assets	576	586
Other current and long-term assets	1	1
Total Assets	1,044	1,049
LIABILITIES
Accounts payable and accrued current liabilities	26	19
Current portion long-term debt, including capital leases	0	0
Mortgage bonds, notes, and other	0	0
Other current and long-term liabilities	1	2
Total liabilities	$ 27	21
VIE ownership and non-ownership percentage	100.00%
VIE ownership percentage	55.00%
Other
ASSETS
Cash and cash equivalents	$ 13	27
Restricted cash	8	7
Accounts receivable	30	34
Inventories	84	112
Property, plant, and equipment, net	70	76
Goodwill	0	0
Intangible assets	0	0
Other current and long-term assets	0	1
Total Assets	205	257
LIABILITIES
Accounts payable and accrued current liabilities	29	32
Current portion long-term debt, including capital leases	3	5
Mortgage bonds, notes, and other	2	5
Other current and long-term liabilities	15	15
Total liabilities	$ 49	$ 57