Balance Sheet Components Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 1	$ 4	$ 3
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	4	15	12
Interest cost	8	8	24	25
Expected return on plan assets	(10)	(10)	(31)	(30)
Amortization of net actuarial loss	4	3	12	9
Net periodic benefit cost	$ 7	$ 5	$ 20	$ 16