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MARKETABLE SECURITIES (Tables) | 6 Months Ended
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Jun. 30, 2025
Investments, Debt and Equity Securities [Abstract] |
Summary of Available-for-Sale Debt Securities | The following is a summary of available-for-sale debt securities, which are held in CYAPC’s and YAEC’s spent nuclear fuel trusts:
| As of June 30, 2025 |  | As of December 31, 2024
Eversource (Millions of Dollars) | Amortized Cost |  | Pre-Tax Unrealized Gains |  | Pre-Tax Unrealized Losses |  | Fair Value |  | Amortized Cost |  | Pre-Tax Unrealized Gains |  | Pre-Tax Unrealized Losses |  | Fair Value
Debt Securities | $ | 162.4 |  |  | $ | 0.1 |  |  | $ | (5.7) |  |  | $ | 156.8 |  |  | $ | 163.2 |  |  | $ | 0.1 |  |  | $ | (6.1) |  |  | $ | 157.2 |
Contractual Maturities of Available-for-Sale Debt Securities | As of June 30, 2025, the contractual maturities of available-for-sale debt securities were as follows:
Eversource (Millions of Dollars) | Amortized Cost |  | Fair Value
Less than one year | $ | 15.1 |  |  | $ | 15.1 |
One to five years | 33.3 |  |  | 33.6 |
Six to ten years | 30.4 |  |  | 30.1 |
Greater than ten years | 83.6 |  |  | 78.0 |
Total Debt Securities | $ | 162.4 |  |  | $ | 156.8 |
Marketable Securities Recorded at Fair Value on a Recurring Basis by Level | The following table presents the marketable securities recorded at fair value on a recurring basis by the level in which they are classified within the fair value hierarchy:
Eversource (Millions of Dollars) | As of June 30, 2025 |  | As of December 31, 2024
Level 1: |  |  |
Mutual Funds and Equities | $ | 159.8 |  |  | $ | 163.1 |
Money Market Funds | 11.7 |  |  | 10.0 |
Total Level 1 | $ | 171.5 |  |  | $ | 173.1 |
Level 2: |  |  |
U.S. Government Issued Debt Securities (Agency and Treasury) | $ | 83.0 |  |  | $ | 92.0 |
Corporate Debt Securities | 39.4 |  |  | 32.5 |
Asset-Backed Debt Securities | 8.0 |  |  | 7.8 |
Municipal Bonds | 6.3 |  |  | 6.8 |
Other Fixed Income Securities | 8.4 |  |  | 8.1 |
Total Level 2 | $ | 145.1 |  |  | $ | 147.2 |
Total Marketable Securities | $ | 316.6 |  |  | $ | 320.3 |

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