Commitments and Contingencies, Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Held Under Capital Leases, Net [Abstract]
Property held under capital lease	$ 222	$ 222
Accumulated depreciation	(77)	(71)
Total property held under capital leases, net	145	151
Capital Leases, Future Minimum Payments Due [Abstract]
2019	14
2020	14
2021	14
2022	12
2023	12
Thereafter	220
Total minimum obligation	286
Interest component of obligation	(201)
Present value of minimum obligation	$ 85
Operating Leased Assets [Line Items]
Operating Lease Purchase Power Agreement Expiration Date	2034
Operating Leases, Future Minimum Payments Due [Abstract]
2019	$ 239
2020	234
2021	235
2022	221
2023	208
Thereafter	1,037
Office Space and Other Equipment [Member]
Operating Leases [Abstract]
Total expenses under operating lease obligations	248	246	$ 255
Operating Leases, Future Minimum Payments Due [Abstract]
2019	32
2020	26
2021	25
2022	24
2023	22
Thereafter	$ 154
WYCO Totem Gas Storage Facilities
Capital Leases [Abstract]
Ownership interest in joint venture (in hundredths)	50.00%
Percentage of the capital lease obligation related to WYCO eliminated (in hundredths)	50.00%
Gas Storage Facilities
Property Held Under Capital Leases, Net [Abstract]
Property held under capital lease	$ 201	201
Gas Pipeline
Property Held Under Capital Leases, Net [Abstract]
Property held under capital lease	21	21
Purchased Power Agreements
Operating Leases [Abstract]
Payments for capacity	210	$ 210	$ 216
Operating Leases, Future Minimum Payments Due [Abstract]
2019	207
2020	208
2021	210
2022	197
2023	186
Thereafter	$ 883