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Basis of Presentation (Details) shares in Millions, $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2016 USD ($) | Mar. 31, 2015 USD ($) | Sep. 30, 2014 USD ($) | Jun. 30, 2016 USD ($) mi² retail_customers shares | Jun. 30, 2015 USD ($) | Dec. 31, 2015 USD ($)
Basis of Presentation [Abstract] |  |  |  |  |  |
Regulatory deferral of settled derivative instruments |  |  |  |  | $ 2 |
Service Area Sq Miles | mi² |  |  |  | 4,000 |  |
Incorporated Cities |  |  |  | 52 |  |
Number of Retail Customers | retail_customers |  |  |  | 859,497 |  |
Service Area Population | shares |  |  |  | 1.8 |  |
Percent of State's Population |  |  |  | 46.00% |  |
Other Comprehensive Income |  | $ 0 |  | $ 0 |  |
Unamortized Debt Issuance Expense |  |  |  | $ 12 |  | $ 11

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- Definition Gain (loss) related to the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one party, or a failure to perform. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 + Details
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