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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 |  |

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- Definition Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84164758&loc=d3e45014-112735 + Details
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- Definition Amount of minimum lease payments for capital leases. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737 + Details
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