Other Income and Expense - Other Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Other Nonoperating Income (Expense) [Line Items]
Gain (Loss) on Disposition of Assets			$ (23)	$ (19)
Allowance for Funds Used During Construction, Capitalized Interest	$ 5	$ 4	12	6
Other Nonoperating Income	7	5	19	19
Other Income	13	12	43	56
Other Income [Member]
Schedule of Other Nonoperating Income (Expense) [Line Items]
Gain (Loss) on Disposition of Assets	1	3	12	13
Altai [Domain]
Schedule of Other Nonoperating Income (Expense) [Line Items]
Reversal Of Legal Contingency	$ 0	$ 0	$ 0	$ 18