v3.25.1
Investments (Tables)
 3 Months Ended
Mar. 31, 2025
Investments, Debt and Equity Securities [Abstract]  
Available-For-Sale Investments The following tables summarize the Company's available-for-sale investments. Agency mortgage-backed securities include securities issued by U.S. government-sponsored enterprises and U.S. government agencies. The net unrealized holding gains (losses) in the tables below are presented before taxes.
 March 31, 2025
(dollars in thousands)Amortized
Cost		Gross
Unrealized
Holding
Gains		Gross
Unrealized
Holding
Losses		Estimated
Fair
Value
Fixed maturity securities:
U.S. Treasury securities$5,257,869 $39,374 $(33,562)$5,263,681 
U.S. government-sponsored enterprises1,495,738 11,133 (77,553)1,429,318 
Obligations of states, municipalities and political subdivisions3,777,894 15,465 (153,987)3,639,372 
Foreign governments, agencies and supranationals
3,067,330 26,273 (160,800)2,932,803 
Agency mortgage-backed securities
2,776,864 13,005 (90,997)2,698,872 
Non-agency mortgage-backed securities
104,737 — (2,783)101,954 
Corporate and university bonds
236,169 268 (24,808)211,629 
Total fixed maturity securities16,716,601 105,518 (544,490)16,277,629 
Short-term investments2,101,050 371 (2,388)2,099,033 
Investments, available-for-sale$18,817,651 $105,889 $(546,878)$18,376,662 

 December 31, 2024
(dollars in thousands)Amortized
Cost		Gross
Unrealized
Holding
Gains		Gross
Unrealized
Holding
Losses		Estimated
Fair
Value
Fixed maturity securities:
U.S. Treasury securities$5,147,365 $8,962 $(68,469)$5,087,858 
U.S. government-sponsored enterprises1,445,171 2,976 (101,911)1,346,236 
Obligations of states, municipalities and political subdivisions3,813,146 5,866 (199,520)3,619,492 
Foreign governments, agencies and supranationals
2,909,561 4,264 (207,302)2,706,523 
Agency mortgage-backed securities
2,771,589 2,096 (123,872)2,649,813 
Non-agency mortgage-backed securities
122,373 — (4,343)118,030 
Corporate and university bonds
248,518 76 (31,007)217,587 
Total fixed maturity securities16,457,723 24,240 (736,424)15,745,539 
Short-term investments2,530,941 548 (6,579)2,524,910 
Investments, available-for-sale$18,988,664 $24,788 $(743,003)$18,270,449 
Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position The following tables summarize gross unrealized investment losses on available-for-sale investments by the length of time that securities have continuously been in an unrealized loss position.
March 31, 2025
Less than 12 months12 months or longerTotal
(dollars in thousands)Estimated
Fair
Value		Gross
Unrealized
Holding Losses		Estimated
Fair
Value		Gross
Unrealized
Holding Losses		Estimated
Fair
Value
Gross
Unrealized
Holding
Losses
Fixed maturity securities:
U.S. Treasury securities$683,847 $(4,986)$1,277,393 $(28,576)$1,961,240 $(33,562)
U.S. government-sponsored enterprises243,333 (3,966)713,889 (73,587)957,222 (77,553)
Obligations of states, municipalities and political subdivisions598,623 (6,410)2,050,569 (147,577)2,649,192 (153,987)
Foreign governments, agencies and supranationals
585,664 (11,664)1,268,147 (149,136)1,853,811 (160,800)
Agency mortgage-backed securities
162,695 (3,264)1,631,014 (87,733)1,793,709 (90,997)
Non-agency mortgage-backed securities
— — 101,954 (2,783)101,954 (2,783)
Corporate and university bonds
— — 202,002 (24,808)202,002 (24,808)
Total fixed maturity securities2,274,162 (30,290)7,244,968 (514,200)9,519,130 (544,490)
Short-term investments1,879,046 (2,388)— — 1,879,046 (2,388)
Total$4,153,208 $(32,678)$7,244,968 $(514,200)$11,398,176 $(546,878)

At March 31, 2025, the Company held 1,225 available-for-sale securities in an unrealized loss position with a total estimated fair value of $11.4 billion and gross unrealized losses of $546.9 million. Of these 1,225 securities, 932 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $7.2 billion and gross unrealized losses of $514.2 million.

December 31, 2024
Less than 12 months12 months or longerTotal
(dollars in thousands)Estimated
Fair
Value
Gross
Unrealized
Holding
Losses
Estimated
Fair
Value
Gross
Unrealized
Holding 
Losses
Estimated
Fair
Value
Gross
Unrealized
Holding 
Losses
Fixed maturity securities:
U.S. Treasury securities$1,593,711 $(27,213)$1,444,869 $(41,256)$3,038,580 $(68,469)
U.S. government-sponsored enterprises415,333 (10,938)691,781 (90,973)1,107,114 (101,911)
Obligations of states, municipalities and political subdivisions1,133,275 (21,242)2,024,298 (178,278)3,157,573 (199,520)
Foreign governments, agencies and supranationals
1,056,877 (29,890)1,246,215 (177,412)2,303,092 (207,302)
Agency mortgage-backed securities
757,562 (13,880)1,710,436 (109,992)2,467,998 (123,872)
Non-agency mortgage-backed securities
— — 118,030 (4,343)118,030 (4,343)
Corporate and university bonds
2,107 (137)212,404 (30,870)214,511 (31,007)
Total fixed maturity securities4,958,865 (103,300)7,448,033 (633,124)12,406,898 (736,424)
Short-term investments163,503 (6,579)— — 163,503 (6,579)
Total$5,122,368 $(109,879)$7,448,033 $(633,124)$12,570,401 $(743,003)

At December 31, 2024, the Company held 1,485 available-for-sale securities in an unrealized loss position with a total estimated fair value of $12.6 billion and gross unrealized losses of $743.0 million. Of these 1,485 securities, 966 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $7.4 billion and gross unrealized losses of $633.1 million.
Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date The amortized cost and estimated fair value of fixed maturity securities at March 31, 2025 are shown below by contractual maturity.
(dollars in thousands)Amortized
Cost		Estimated
Fair Value
Due in one year or less$1,584,937 $1,568,859 
Due after one year through five years6,422,711 6,349,767 
Due after five years through ten years4,657,827 4,511,211 
Due after ten years1,169,525 1,046,966 
13,835,000 13,476,803 
Mortgage-backed securities
2,881,601 2,800,826 
Total fixed maturity securities$16,716,601 $16,277,629 
Components Of Net Investment Income The following table presents the components of net investment income.
Three Months Ended March 31,
(dollars in thousands)20252024
Interest:
Fixed maturity securities$143,345 $119,476 
Short-term investments19,673 32,184 
Cash and cash equivalents and restricted cash and cash equivalents
39,774 39,078 
Dividends on equity securities40,195 32,693 
242,987 223,431 
Investment expenses(5,892)(5,162)
Net investment income
$237,095 $218,269 
Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Available-For-Sale Investments The following table presents the components of net investment gains (losses) included in net income and the change in net unrealized losses included in other comprehensive income (loss). Gross realized investment gains and losses on fixed maturity securities, short-term investments and other investments were not material to the consolidated financial statements and are presented on a net basis in the following table.
Three Months Ended March 31,
(dollars in thousands)20252024
Fixed maturity securities, short-term investments and other investments:
Net realized investment losses$(1,801)$(4,488)
Equity securities:
Change in fair value of securities sold during the period(1,322)43 
Change in fair value of securities held at the end of the period(145,948)906,726 
Total change in fair value(147,270)906,769 
Net investment gains (losses)$(149,071)$902,281 
Change in net unrealized losses on available-for-sale investments included in other comprehensive income (loss):
Fixed maturity securities$273,213 $(148,487)
Short-term investments4,014 (7,282)
Net increase (decrease)$277,227 $(155,769)