Other Income and Expense - Other Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Other Nonoperating Income [Line Items]
Other income	$ 12	$ 15	$ 25	$ 30
Other Income [Member]
Schedule of Other Nonoperating Income [Line Items]
Public Utilities, Allowance for Funds Used During Construction, Additions	7	3	14	7
Gain On Sale Of Assets	1	6	3	11
Other Nonoperating Income	$ 4	$ 6	$ 8	$ 12