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Balance Sheet Components Balance Sheet Components (Policies) | 6 Months Ended
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Jun. 30, 2018
Balance Sheet Components [Abstract] |
Inventory, Policy [Policy Text Block] | Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of June 30, 2018 and December 31, 2017 (dollars in thousands):
| June 30, |  | December 31,
| 2018 |  | 2017
Materials and supplies | $ | 44,335 |  |  | $ | 41,493 |
Fuel stock | 5,958 |  |  | 4,843 |
Stored natural gas | 6,608 |  |  | 11,739 |
Total | $ | 56,901 |  |  | $ | 58,075 |

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- Definition Disclosure of inventory accounting policy for inventory classes, including, but not limited to, basis for determining inventory amounts, methods by which amounts are added and removed from inventory classes, loss recognition on impairment of inventories, and situations in which inventories are stated above cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66092785&loc=d3e4492-108314 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=66092785&loc=d3e4556-108314 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766 + Details
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