Balance Sheet Components Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2	$ 1	$ 3	$ 2
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	4	10	8
Interest cost	8	9	16	17
Expected return on plan assets	(11)	(10)	(21)	(20)
Amortization of net actuarial loss	4	3	8	6
Net periodic benefit cost	$ 6	$ 6	$ 13	$ 11