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Financing: At-the-Market Equity Offering Program (Details) - Common Stock - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Proceeds, (net of issuance costs) | $ 108.6 | $ 52.8 | $ 181.6 | $ 107.7
Average price per share | $ 56.84 | $ 57.33 | $ 55.63 | $ 60.02
Number of shares issued | 1.9 | 0.9 | 3.3 | 1.8
Payments of Stock Issuance Costs | $ (1.1) | $ (0.5) | $ (1.8) | $ (1.1)
August 4, 2020 ATM Program |  |  |  |
Proceeds, (net of issuance costs) | $ 0.0 | $ 0.0 | $ 0.0 | $ 48.5
Number of shares issued | 0.0 | 0.0 | 0.0 | 0.8
Payments of Stock Issuance Costs | $ 0.0 | $ 0.0 | $ 0.0 | $ (0.5)
June 16, 2023 ATM Program |  |  |  |
Proceeds, (net of issuance costs) | $ 108.6 | $ 52.8 | $ 181.6 | $ 59.2
Number of shares issued | 1.9 | 0.9 | 3.3 | 1.0
Payments of Stock Issuance Costs | $ (1.1) | $ (0.5) | $ (1.8) | $ (0.6)

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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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