v3.26.3
Investments (Tables)
 9 Months Ended
Sep. 30, 2026
Investments, Debt and Equity Securities [Abstract]  
Schedule of Debt Securities, Available-for-Sale
The following table summarizes the fair value of fixed maturity investments:
September 30, 2026
Amortized CostUnrealized
gains		Unrealized
losses		Fair
value
U.S. Treasuries$343.0 $— $(6.7)$336.3 
Non-U.S. government39.1 — (0.5)38.6 
Corporate bonds1,730.7 1.5 (34.3)1,697.9 
Residential mortgage-backed428.8 0.1 (4.5)424.4 
Commercial mortgage-backed10.3 — (0.2)10.1 
Other asset-backed securities287.2 0.3 (2.1)285.4 
Total fixed maturity securities$2,839.1 $1.9 $(48.3)$2,792.7 
December 31, 2025
Amortized CostUnrealized
gains		Unrealized
losses		Fair
value
U.S. Treasuries$477.8 $6.6 $(0.2)$484.2 
Agencies6.9 — — 6.9 
Non-U.S. government46.6 0.6 — 47.2 
Corporate bonds1,616.8 35.7 (0.3)1,652.2 
Residential mortgage-backed244.3 5.6 — 249.9 
Commercial mortgage-backed1.0 — — 1.0 
Other asset-backed securities197.2 1.9 (0.1)199.0 
Total fixed maturity securities$2,590.6 $50.4 $(0.6)$2,640.4 
The composition of the fair values of fixed maturity securities by credit rating is as follows:
September 30, 2026December 31, 2025
Fair Value%Fair Value%
AAA$286.1 10%$216.1 9%
AA886.1 32%891.2 34%
A1,182.2 42%1,118.8 42%
BBB413.7 15%382.8 14%
Below BBB24.6 1%31.5 1%
Total fixed maturity securities$2,792.7 100%$2,640.4 100%
The contractual maturities for fixed maturity securities are listed in the following table:
September 30, 2026December 31, 2025
Amortized CostFair ValueAmortized CostFair Value
Due in one year or less$145.6 $145.8 $233.0 $234.2 
Due after one year through five years1,513.7 1,496.8 1,503.5 1,532.4 
Due after five years through ten years623.5 602.4 520.3 534.3 
Due after ten years556.3 547.7 333.8 339.5 
Total fixed maturity securities$2,839.1 $2,792.7 $2,590.6 $2,640.4 
The Company’s short-term investments consist of U.S. Treasuries, corporate bonds and other asset-backed securities with maturities of 90 days or greater but less than one year at the time of purchase:
September 30, 2026
Amortized CostUnrealized
gains		Unrealized
losses		Fair
value
U.S. Treasuries$267.3 $— $(0.4)$266.9 
Corporate bonds1.4 — — 1.4 
Other asset-backed securities0.4 — — 0.4 
Total short-term investments
$269.1 $— $(0.4)$268.7 
December 31, 2025
Amortized CostUnrealized
gains		Unrealized
losses		Fair
value
U.S. Treasuries$109.9 $— $— $109.9 
Corporate bonds1.0 — — 1.0 
Other asset-backed securities0.4 — — 0.4 
Total short-term investments
$111.3 $— $— $111.3 
The composition of the fair values of short-term investments by credit rating is as follows:
September 30, 2026December 31, 2025
Fair Value%Fair Value%
AAA$0.4 —%$0.4 —%
AA266.9 100%109.9 99%
A0.8 —%0.7 1%
BBB0.6 —%0.3 —%
Total short-term investments$268.7 100%$111.3 100%
Schedule of Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value
The following table summarizes, by type of security, the aggregate fair value and gross unrealized loss by length of time the security has been in an unrealized loss position for the Company’s available-for-sale portfolio:
September 30, 2026
0 - 12 months> 12 months
Fair
value		Gross unrealized lossesGross unrealized lossesNumber of securities
U.S. Treasuries$552.4 $(7.1)$— 169 
Non-U.S. government35.5 (0.5)— 26 
Corporate bonds1,290.7 (34.2)(0.1)957 
Residential mortgage-backed262.7 (4.5)— 113 
Commercial mortgage-backed8.3 (0.2)— 14 
Other asset-backed securities181.5 (2.1)— 110 
Total$2,331.1 $(48.6)$(0.1)1,389 
December 31, 2025
0 - 12 months> 12 months
Fair
value		Gross unrealized lossesGross unrealized lossesNumber of securities
U.S. Treasuries$50.1 $(0.1)$(0.1)49 
Non-U.S. government5.3 — — 3 
Corporate bonds53.3 (0.3)— 132 
Residential mortgage-backed2.2 — — 1 
Other asset-backed securities25.3 (0.1)— 30 
Total$136.2 $(0.5)$(0.1)215 
Schedule of Allowance for Expected Credit Losses
The following table provides a roll forward of the allowance for expected credit losses of the Company’s securities classified as available-for-sale:
Three months endedNine months ended
September 30,
2026		September 30, 2025September 30,
2026		September 30, 2025
Balance at beginning of period$3.6 $0.6 $0.6 $5.9 
Expected credit losses on securities where credit losses were not previously recognized10.6 0.4 14.5 1.1 
Additions/(reductions) for expected credit losses on securities where credit losses were previously recognized5.4 (0.6)5.2 (5.8)
Securities sold/redeemed/matured(0.3)(0.1)(1.0)(0.9)
Balance at end of period$19.3 $0.3 $19.3 $0.3 
Schedule of Other Investments at Fair Value
The following table provides a summary of the Company’s other investments by investment strategy:
September 30, 2026December 31, 2025
Fair Value%Fair Value%
Fixed income funds$272.8 41%$243.0 50%
Hedge funds
Credit25.7 3%25.0 5%
Global macro49.7 8%41.6 9%
Long/short189.5 29%67.4 14%
Multi-strategy and event-driven99.3 15%96.8 20%
Total hedge funds364.2 55%230.8 48%
Private credit funds24.54%11.92%
Total other investments$661.5 100%$485.7 100%
Schedule of Components of Net Investment Return
The components of net investment return are as follows:
Three Months EndedNine Months Ended
September 30,
2026		September 30, 2025September 30,
2026		September 30, 2025
Net interest and dividend income$45.8 $47.9 $137.4 $146.2 
Investment expenses(1.2)(2.0)(5.1)(6.2)
Net investment income44.6 45.9 132.3 140.0 
Net realized gains/(losses) on fixed maturity securities, available-for-sale(2.7)1.3 (3.4)2.9 
Net realized gain on derivatives— — 0.1 — 
Net realized and unrealized gains/(losses) on other investments(9.0)4.7 17.9 10.4 
Change in net unrealized losses on derivatives— (0.1)— (0.1)
Change in provision for expected credit losses (15.7)0.3 (18.7)5.6 
Net realized and unrealized investment gains/(losses)(27.4)6.2 (4.1)18.8 
Total realized and unrealized investment gains/(losses) and net investment income$17.2 $52.1 $128.2 $158.8