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Financing: At-the-Market Equity Offering Program (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Number of shares issued | 930,844 |  | 1,812,624 | 272,592
August 4, 2020 ATM Program |  |  |  |
Number of shares issued |  |  | 775,225 | 272,592
June 16, 2023 ATM Program |  |  |  |
Number of shares issued | 930,844 |  | 1,037,399 |
Common Stock |  |  |  |
Proceeds, (net of issuance costs) | $ 52.8 |  | $ 107.7 | $ 20.2
Average price per share | $ 57.33 |  | $ 60.02 | $ 74.84
Payments of Stock Issuance Costs | $ (0.5) | $ 0.0 | $ (1.1) | $ (0.2)
Common Stock | August 4, 2020 ATM Program |  |  |  |
Proceeds, (net of issuance costs) |  |  | 48.5 | 20.2
Payments of Stock Issuance Costs | 0.0 | 0.0 | (0.5) | (0.2)
Common Stock | June 16, 2023 ATM Program |  |  |  |
Proceeds, (net of issuance costs) | 52.8 |  | 59.2 |
Payments of Stock Issuance Costs | $ (0.5) | $ 0.0 | $ (0.6) | $ 0.0

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- Definition The cash outflow for cost incurred directly with the issuance of an equity security. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-15 + Details
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