Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 62	$ 92	$ 32	$ 37
Restricted cash	22	21
Accounts receivable	1,451	1,522
Property, plant, and equipment, net	20,063	19,730
Goodwill	2,291	2,286
Intangible assets	890	842
Total Assets	32,582	32,041
LIABILITIES
Current portion long-term debt, including capital leases	412	14
Mortgage bonds, notes, and other	10,600	10,506
Variable interest entity, primary beneficiary, restricted
ASSETS
Cash and cash equivalents	48	63
Restricted cash	7	7
Accounts receivable	45	42
Inventories	65	115
Property, plant, and equipment, net	466	474
Goodwill	22	17
Intangible assets	580	586
Other current and long-term assets	1	2
Total Assets	1,234	1,306
LIABILITIES
Accounts payable and accrued current liabilities	57	51
Current portion long-term debt, including capital leases	4	5
Mortgage bonds, notes, and other	3	5
Other current and long-term liabilities	17	17
Total liabilities	81	78
SGG
ASSETS
Cash and cash equivalents	33	36
Restricted cash	0	0
Accounts receivable	9	8
Inventories	3	3
Property, plant, and equipment, net	395	398
Goodwill	22	17
Intangible assets	580	586
Other current and long-term assets	1	1
Total Assets	1,043	1,049
LIABILITIES
Accounts payable and accrued current liabilities	20	19
Current portion long-term debt, including capital leases	0	0
Mortgage bonds, notes, and other	0	0
Other current and long-term liabilities	2	2
Total liabilities	$ 22	21
VIE ownership and non-ownership percentage	100.00%
VIE ownership percentage	55.00%
Other
ASSETS
Cash and cash equivalents	$ 15	27
Restricted cash	7	7
Accounts receivable	36	34
Inventories	62	112
Property, plant, and equipment, net	71	76
Goodwill	0	0
Intangible assets	0	0
Other current and long-term assets	0	1
Total Assets	191	257
LIABILITIES
Accounts payable and accrued current liabilities	37	32
Current portion long-term debt, including capital leases	4	5
Mortgage bonds, notes, and other	3	5
Other current and long-term liabilities	15	15
Total liabilities	$ 59	$ 57