v3.25.2
Investments (Tables)
 6 Months Ended
Jun. 30, 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.
 June 30, 2025
(dollars in thousands)Amortized
Cost		Gross
Unrealized
Holding
Gains		Gross
Unrealized
Holding
Losses		Estimated
Fair
Value
Fixed maturity securities:
U.S. Treasury securities$5,474,824 $53,829 $(24,453)$5,504,200 
U.S. government-sponsored enterprises1,576,299 15,402 (68,703)1,522,998 
Obligations of states, municipalities and political subdivisions3,764,932 21,514 (136,284)3,650,162 
Foreign governments, agencies and supranationals
3,090,058 109,023 (73,786)3,125,295 
Agency mortgage-backed securities
2,747,479 18,940 (79,158)2,687,261 
Non-agency mortgage-backed securities
71,621 — (1,264)70,357 
Corporate and university bonds
234,361 176 (22,402)212,135 
Total fixed maturity securities16,959,574 218,884 (406,050)16,772,408 
Short-term investments1,890,017 4,760 (253)1,894,524 
Investments, available-for-sale$18,849,591 $223,644 $(406,303)$18,666,932 

 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 
Unrealized Gain (Loss) on Investments 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.
June 30, 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$533,367 $(2,494)$1,301,162 $(21,959)$1,834,529 $(24,453)
U.S. government-sponsored enterprises233,480 (3,935)717,259 (64,768)950,739 (68,703)
Obligations of states, municipalities and political subdivisions494,098 (5,135)1,994,681 (131,149)2,488,779 (136,284)
Foreign governments, agencies and supranationals
137,638 (1,344)1,176,691 (72,442)1,314,329 (73,786)
Agency mortgage-backed securities
218,371 (2,544)1,493,447 (76,614)1,711,818 (79,158)
Non-agency mortgage-backed securities
— — 70,357 (1,264)70,357 (1,264)
Corporate and university bonds
— — 186,421 (22,402)186,421 (22,402)
Total fixed maturity securities1,616,954 (15,452)6,940,018 (390,598)8,556,972 (406,050)
Short-term investments1,167,109 (253)— — 1,167,109 (253)
Total$2,784,063 $(15,705)$6,940,018 $(390,598)$9,724,081 $(406,303)

At June 30, 2025, the Company held 1,085 available-for-sale securities in an unrealized loss position with a total estimated fair value of $9.7 billion and gross unrealized losses of $406.3 million. Of these 1,085 securities, 885 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $6.9 billion and gross unrealized losses of $390.6 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 June 30, 2025 are shown below by contractual maturity.
(dollars in thousands)Amortized
Cost		Estimated
Fair Value
Due in one year or less$1,899,807 $1,900,181 
Due after one year through five years6,347,802 6,376,686 
Due after five years through ten years4,723,348 4,674,790 
Due after ten years1,169,517 1,063,133 
14,140,474 14,014,790 
Mortgage-backed securities
2,819,100 2,757,618 
Total fixed maturity securities$16,959,574 $16,772,408 
Components Of Net Investment Income The following table presents the components of net investment income.
Quarter Ended June 30, Six Months Ended June 30,
(dollars in thousands)2025202420252024
Interest:
Fixed maturity securities$145,829 $121,189 $289,174 $240,665 
Short-term investments19,580 31,654 39,253 63,838 
Cash and cash equivalents and restricted cash and cash equivalents
35,723 42,542 75,497 81,620 
Dividends on equity securities34,812 31,831 75,007 64,524 
235,944 227,216 478,931 450,647 
Investment expenses(5,935)(4,155)(11,827)(9,317)
Net investment income
$230,009 $223,061 $467,104 $441,330 
Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Available-For-Sale Investments The following table presents the components of net investment gains (losses) included in net income and the change in net unrealized losses included in other comprehensive income (loss). Gross realized investment gains and losses on fixed maturity securities, short-term investments and other investments were not material to the consolidated financial statements and are presented on a net basis in the following table.
Quarter Ended June 30, Six Months Ended June 30,
(dollars in thousands)2025202420252024
Fixed maturity securities, short-term investments and other investments:
Net realized investment losses$(16,596)$(14,007)$(18,397)$(18,495)
Equity securities:
Change in fair value of securities sold during the period1,134 (4,654)(188)(4,611)
Change in fair value of securities held at the end of the period595,685 (111,356)449,737 795,370 
Total change in fair value596,819 (116,010)449,549 790,759 
Net investment gains (losses)$580,223 $(130,017)$431,152 $772,264 
Change in net unrealized losses on available-for-sale investments included in other comprehensive income (loss):
Fixed maturity securities$251,805 $(36,240)$525,018 $(184,727)
Short-term investments6,524 (358)10,538 (7,640)
Net increase (decrease)$258,329 $(36,598)$535,556 $(192,367)