XML 29 R14.htm IDEA: XBRL DOCUMENT
v3.25.4

Investment Income and Gains and Losses | 12 Months Ended
--- | ---
Dec. 31, 2025
Investments, Debt and Equity Securities [Abstract] |
Investment Income and Gains and Losses | 3. INVESTMENT INCOME AND GAINS AND LOSSES A. NET INVESTMENT INCOME The components of net investment income were as follows:
YEARS ENDED DECEMBER 31 |  | 2025 |  |  | 2024 |  |  | 2023 |
(in millions) |  |  |  |  |  |  |  |  |
Fixed maturities |  | $ | 401.4 |  |  | $ | 324.4 |  |  | $ | 283.2 |
Limited partnerships |  |  | 27.1 |  |  |  | 20.6 |  |  |  | 30.0 |
Mortgage loans |  |  | 11.2 |  |  |  | 14.4 |  |  |  | 15.8 |
Equity securities |  |  | 3.6 |  |  |  | 3.2 |  |  |  | 6.4 |
Short-term and other investments |  |  | 26.4 |  |  |  | 25.2 |  |  |  | 10.6 |
Gross investment income |  |  | 469.7 |  |  |  | 387.8 |  |  |  | 346.0 |
Less: investment expenses |  |  | (15.3 | ) |  |  | (15.2 | ) |  |  | (13.9 | )
Net investment income |  | $ | 454.4 |  |  | $ | 372.6 |  |  | $ | 332.1 |
The change in fair value of limited partnerships measured using NAV is reported in net investment income, of which holding losses of $10.0 million, $8.3 million and $8.1 million were related to securities owned at December 31, 2025, 2024 and 2023, respectively. We held no fixed maturity securities or mortgages loans on non-accrual status at December 31, 2025 and 2024. The carrying value of fixed maturity securities on non-accrual status was $14.8 million at December 31, 2023. The effects on income of non-accruals compared with amounts that would have been recognized in accordance with the original terms of the fixed maturities were not material for the years ended December 31, 2025, 2024 and 2023. B. NET REALIZED AND UNREALIZED INVESTMENT GAINS AND LOSSES Net realized and unrealized gains (losses) on investments, including impairments, were as follows:
YEARS ENDED DECEMBER 31 |  | 2025 |  |  | 2024 |  |  | 2023 |
(in millions) |  |  |  |  |  |  |  |  |
Fixed maturities |  | $ | (61.8 | ) |  | $ | (89.6 | ) |  | $ | (20.2 | )
Equity securities |  |  | 19.0 |  |  |  | 14.2 |  |  |  | (5.6 | )
Mortgage loans |  |  | (2.5 | ) |  |  | (0.5 | ) |  |  | (6.9 | )
Other investments |  |  | (0.7 | ) |  |  | 0.1 |  |  |  | 0.2 |
Net realized and unrealized investment losses |  | $ | (46.0 | ) |  | $ | (75.8 | ) |  | $ | (32.5 | )
The following table provides pre-tax net realized and unrealized gains (losses) on equity securities recognized in income:
YEARS ENDED DECEMBER 31 |  | 2025 |  |  | 2024 |  |  | 2023 |
(in millions) |  |  |  |  |  |  |  |  |
On securities still held |  | $ | 18.4 |  |  | $ | 14.2 |  |  | $ | 6.0 |
On securities sold during the period |  |  | 0.6 |  |  |  | — |  |  |  | (11.6 | )
Total net realized and unrealized gains (losses) on equity securities recognized in income |  | $ | 19.0 |  |  | $ | 14.2 |  |  | $ | (5.6 | )
Impairments Included in net realized and unrealized investment losses for the years ended December 31, 2025, 2024 and 2023, were net impairment losses of $3.1 million, $5.8 million and $18.0 million, respectively. In 2025, net impairment losses primarily related to mortgage loans. In 2024, net impairment losses consisted of $4.1 million on mortgage loans and $1.7 million on fixed maturities. In 2023, net impairment losses consisted of $11.1 million on fixed maturities, primarily related to intent to sell securities, and $6.9 million of estimated credit losses on mortgage loans. At December 31, 2025 and 2024, the allowance for credit losses on mortgage loans was $8.1 million and $5.7 million, respectively, and the allowance for credit losses on available-for-sale securities was not material. The following table provides rollforwards of the allowance for credit losses on mortgage loans:
YEARS ENDED DECEMBER 31 |  | 2025 |  |  | 2024 |
(in millions) |  |  |  |  |  |
Allowance for credit losses as of the beginning of the period |  | $ | 5.7 |  |  | $ | 10.0 |
Reductions for disposals |  |  | (0.5 | ) |  |  | (3.6 | )
Reductions for writedowns |  |  | — |  |  |  | (3.0 | )
Additional credit losses on investments for which an allowance was previously recognized |  |  | 2.9 |  |  |  | 2.3 |
Allowance for credit losses as of the end of the period |  | $ | 8.1 |  |  | $ | 5.7 |
The methodology and significant inputs used to measure the amount of credit losses were as follows: Mortgage loans – the Company estimated losses by applying expected loss rates, which are based on historical data. Embedded in expected loss rates are mortgage risk ratings and risk factors associated with property type such as office, retail, lodging, multi-family and industrial. Risk ratings, based on property characteristics and metrics including the geographic market, are predominantly driven by estimates of loan-to-value and debt service coverage ratios. Ratings may be adjusted to reflect current conditions and to incorporate reasonable and supportable forecasts, such as volatility of cash flows and valuation. Fixed maturities, Corporate bonds – the Company utilized a financial model that derives expected cash flows based on probability-of-default factors by credit rating and asset duration, and loss-given-default factors based on security type. These factors are based on historical data provided by an independent third-party rating agency. In addition, other qualitative market data relevant to the realizability of contractual cash flows may be considered, including current conditions and reasonable and supportable forecasts. The proceeds from sales of available-for-sale fixed maturities, and the gross realized gains and gross realized losses on those sales, were as follows:
YEARS ENDED DECEMBER 31 |  | 2025 |  |  | 2024 |  |  | 2023 |
(in millions) |  |  |  |  |  |  |  |  |
Proceeds from sales |  | $ | 1,452.9 |  |  | $ | 1,844.1 |  |  | $ | 168.8 |
Gross gains |  |  | 2.4 |  |  |  | 2.5 |  |  |  | 1.0 |
Gross losses |  |  | 64.6 |  |  |  | 91.3 |  |  |  | 10.5 |

X
- Definition Investment income and gains and losses disclosure. + References No definition available. + Details
Name: | thg_InvestmentIncomeAndGainsAndLossesDisclosureTextBlock
Namespace Prefix: | thg_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration