EBP Net Periodic Benefit Cost & OCI (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Components of net periodic benefit cost (credit):
Service cost	$ 50	$ 50	$ 54
Interest cost	46	59	62
Expected return on plan assets	(63)	(82)	(85)
Amortization of prior service credit	0	0	0
Amortization of net actuarial loss	23	27	30
Net actuarial loss from settlements	23	71	2
Reclassification to regulatory liability	0	0	0
Net periodic benefit cost (credit)	79	125	63
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss):
Net actuarial gain (loss)	(18)	62	(23)
Amortization of prior service credit	0	0	0
Amortization of net actuarial loss	23	27	30
Net actuarial loss from settlements	23	71	2
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss)	28	160	9
Other Postretirement Benefits [Member]
Components of net periodic benefit cost (credit):
Service cost	1	1	1
Interest cost	7	8	8
Expected return on plan assets	(11)	(11)	(12)
Amortization of prior service credit	(2)	(13)	(15)
Amortization of net actuarial loss	0	0	0
Net actuarial loss from settlements	0	0	0
Reclassification to regulatory liability	2	3	4
Net periodic benefit cost (credit)	(3)	(12)	(14)
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss):
Net actuarial gain (loss)	9	(3)	0
Amortization of prior service credit	0	(5)	(6)
Amortization of net actuarial loss	0	0	0
Net actuarial loss from settlements	0	0	0
Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss)	9	(8)	(6)
Other changes in plan assets and benefit obligations recognized in regulatory (assets) and liabilities:
Net actuarial gain (loss)	(10)	6	2
Amortization of prior service credit	(2)	(8)	$ (9)
Other Nonoperating Income (Expense) [Member] | Pension Benefits [Member]
Components of net periodic benefit cost (credit):
Net actuarial loss from settlements	$ 23	$ 71