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Financing: Revolving Credit Facility and CP Program (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2021 | Mar. 31, 2020
Net (payments) borrowings of Revolving Credit Facility and CP Program | $ (18,170) | $ (30,375)
Commercial Paper |  |
Short-term interest rate | 0.23% |

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- Definition Weighted average interest rate of short-term debt outstanding calculated at point in time. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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