Other Income and Expense - Other Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule of Other Nonoperating Income [Line Items]
Other income	$ 13	$ 15
Other Income [Member]
Schedule of Other Nonoperating Income [Line Items]
Allowance for Funds Used During Construction, Capitalized Interest	7	4
Gain On Sale Of Assets	2	5
Other Nonoperating Income	$ 4	$ 6