Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 82	$ 92	$ 35	$ 37
Restricted cash	20	21
Accounts receivable	1,408	1,522
Property, plant, and equipment, net	19,866	19,730
Goodwill	2,292	2,286
Intangible assets	837	842
Total Assets	32,149	32,041
LIABILITIES
Current portion long-term debt, including capital leases	13	14
Mortgage bonds, notes, and other	10,999	10,506
Variable interest entity, primary beneficiary, restricted
ASSETS
Cash and cash equivalents	63	63
Restricted cash	7	7
Accounts receivable	29	42
Inventories	62	115
Property, plant, and equipment, net	472	474
Goodwill	22	17
Intangible assets	583	586
Other current and long-term assets	1	2
Total Assets	1,239	1,306
LIABILITIES
Accounts payable and accrued current liabilities	40	51
Current portion long-term debt, including capital leases	5	5
Mortgage bonds, notes, and other	4	5
Other current and long-term liabilities	16	17
Total liabilities	65	78
Variable interest entity, primary beneficiary, SGG
ASSETS
Cash and cash equivalents	52	36
Restricted cash	0	0
Accounts receivable	10	8
Inventories	3	3
Property, plant, and equipment, net	397	398
Goodwill	22	17
Intangible assets	583	586
Other current and long-term assets	0	1
Total Assets	1,067	1,049
LIABILITIES
Accounts payable and accrued current liabilities	19	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	$ 21	21
VIE ownership and non-ownership percentage	100.00%
VIE ownership percentage	55.00%
Variable interest entity, primary beneficiary other, restricted
ASSETS
Cash and cash equivalents	$ 11	27
Restricted cash	7	7
Accounts receivable	19	34
Inventories	59	112
Property, plant, and equipment, net	75	76
Goodwill	0	0
Intangible assets	0	0
Other current and long-term assets	1	1
Total Assets	172	257
LIABILITIES
Accounts payable and accrued current liabilities	21	32
Current portion long-term debt, including capital leases	5	5
Mortgage bonds, notes, and other	4	5
Other current and long-term liabilities	14	15
Total liabilities	$ 44	$ 57