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CAPITAL CONSTRUCTION FUND (Tables) | 3 Months Ended
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Mar. 31, 2025
CAPITAL CONSTRUCTION FUND |
Schedule of capital construction fund | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended
​ | ​ | March 31,
(In millions) |  | 2025 |  | 2024
CCF Cash and Cash Equivalents: | ​ | ​ | ​ | ​ | ​ | ​
CCF cash and cash equivalents balance at beginning of period | ​ | $ | 230.7 | ​ | $ | 599.4
Cash withdrawal for the purchase of U.S. Treasury debt securities and accrued interest | ​ | ​ | — | ​ | ​ | (449.8)
Proceeds from U.S. Treasury debt securities at maturity | ​ | ​ | 20.3 | ​ | ​ | —
Interest income on cash and cash equivalents, and CCF investments | ​ | ​ | 4.1 | ​ | ​ | 7.2
Repurchase of assigned accounts receivable | ​ | ​ | 100.7 | ​ | ​ | —
Qualifying withdrawal payments out of the CCF | ​ | ​ | (65.0) | ​ | ​ | —
Total CCF cash and cash equivalents balance at end of period | ​ | ​ | 290.8 | ​ | ​ | 156.8
​ | ​ | ​ | ​ | ​ | ​ | ​
CCF Investments: | ​ | ​ | ​ | ​ | ​ | ​
CCF investments balance at beginning of period | ​ | ​ | 411.9 | ​ | ​ | —
Purchase of U.S. Treasury debt securities | ​ | ​ | — | ​ | ​ | 448.1
Withdrawals of U.S. Treasury debt securities at maturity | ​ | ​ | (20.3) | ​ | ​ | —
Accretion of investments | ​ | ​ | 3.0 | ​ | ​ | 1.9
Total CCF investments balance at end of period | ​ | ​ | 394.6 | ​ | ​ | 450.0
Total CCF cash and cash equivalents, and investments balance at end of period | ​ | $ | 685.4 | ​ | $ | 606.8
Schedule of maturities of capital construction fund investments | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | As of
​ | ​ | March 31, 2025
Year (in millions) |  | Cost | ​ | Fair Value
2025 | ​ | $ | 173.0 | ​ | $ | 173.2
2026 | ​ |  | 169.3 | ​ |  | 169.9
2027 | ​ |  | 52.3 | ​ |  | 52.6
Total CCF investments | ​ | $ | 394.6 | ​ | $ | 395.7

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