Balance Sheet Components Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Interest cost			$ 2
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4	$ 4	12	$ 12
Interest cost	8	9	25	25
Expected return on plan assets	(10)	(10)	(30)	(30)
Amortization of net actuarial loss	3	3	9	11
Net periodic benefit cost	$ 5	$ 6	$ 16	$ 18