Investments - Schedule of Unrealized Investment Losses by Class of Investment (Details) - USD ($)
$ in Thousands |
Jun. 30, 2025 |
Dec. 31, 2024 |
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
$ 3,247,642
|
$ 3,886,032
|
| Unrealized Loss, Less than Twelve Months |
(146,780)
|
(183,665)
|
| Fair Value, Twelve Months or Longer |
8,026,266
|
8,001,246
|
| Unrealized Loss, Twelve Months or Longer |
(1,762,873)
|
(1,741,324)
|
| Fair Value |
11,273,908
|
11,887,278
|
| Unrealized Loss |
(1,909,653)
|
(1,924,989)
|
| Investment grade securities: |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
3,209,929
|
3,809,580
|
| Unrealized Loss, Less than Twelve Months |
(145,257)
|
(179,843)
|
| Fair Value, Twelve Months or Longer |
7,708,691
|
7,705,596
|
| Unrealized Loss, Twelve Months or Longer |
(1,705,772)
|
(1,671,119)
|
| Fair Value |
10,918,620
|
11,515,176
|
| Unrealized Loss |
(1,851,029)
|
(1,850,962)
|
| Investment grade securities: | U.S. Government direct, guaranteed, and government-sponsored enterprises |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
4,658
|
11,268
|
| Unrealized Loss, Less than Twelve Months |
(497)
|
(290)
|
| Fair Value, Twelve Months or Longer |
365,241
|
347,527
|
| Unrealized Loss, Twelve Months or Longer |
(30,970)
|
(42,504)
|
| Fair Value |
369,899
|
358,795
|
| Unrealized Loss |
(31,467)
|
(42,794)
|
| Investment grade securities: | States, municipalities, and political subdivisions |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
788,376
|
778,244
|
| Unrealized Loss, Less than Twelve Months |
(47,539)
|
(32,894)
|
| Fair Value, Twelve Months or Longer |
1,449,974
|
1,532,264
|
| Unrealized Loss, Twelve Months or Longer |
(586,385)
|
(501,865)
|
| Fair Value |
2,238,350
|
2,310,508
|
| Unrealized Loss |
(633,924)
|
(534,759)
|
| Investment grade securities: | Foreign governments |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
0
|
0
|
| Unrealized Loss, Less than Twelve Months |
0
|
0
|
| Fair Value, Twelve Months or Longer |
25,084
|
24,925
|
| Unrealized Loss, Twelve Months or Longer |
(9,842)
|
(8,870)
|
| Fair Value |
25,084
|
24,925
|
| Unrealized Loss |
(9,842)
|
(8,870)
|
| Investment grade securities: | Corporates |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
2,410,360
|
2,996,837
|
| Unrealized Loss, Less than Twelve Months |
(97,155)
|
(146,564)
|
| Fair Value, Twelve Months or Longer |
5,848,962
|
5,758,241
|
| Unrealized Loss, Twelve Months or Longer |
(1,077,831)
|
(1,115,789)
|
| Fair Value |
8,259,322
|
8,755,078
|
| Unrealized Loss |
(1,174,986)
|
(1,262,353)
|
| Investment grade securities: | Corporates | Industrials |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
1,295,455
|
1,487,940
|
| Unrealized Loss, Less than Twelve Months |
(63,946)
|
(73,404)
|
| Fair Value, Twelve Months or Longer |
3,437,449
|
3,433,034
|
| Unrealized Loss, Twelve Months or Longer |
(638,215)
|
(690,920)
|
| Fair Value |
4,732,904
|
4,920,974
|
| Unrealized Loss |
(702,161)
|
(764,324)
|
| Investment grade securities: | Corporates | Financial |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
749,725
|
961,932
|
| Unrealized Loss, Less than Twelve Months |
(23,304)
|
(52,946)
|
| Fair Value, Twelve Months or Longer |
1,846,917
|
1,785,130
|
| Unrealized Loss, Twelve Months or Longer |
(346,568)
|
(333,873)
|
| Fair Value |
2,596,642
|
2,747,062
|
| Unrealized Loss |
(369,872)
|
(386,819)
|
| Investment grade securities: | Corporates | Utilities |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
365,180
|
546,965
|
| Unrealized Loss, Less than Twelve Months |
(9,905)
|
(20,214)
|
| Fair Value, Twelve Months or Longer |
564,596
|
540,077
|
| Unrealized Loss, Twelve Months or Longer |
(93,048)
|
(90,996)
|
| Fair Value |
929,776
|
1,087,042
|
| Unrealized Loss |
(102,953)
|
(111,210)
|
| Investment grade securities: | Other asset-backed securities |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
6,535
|
23,231
|
| Unrealized Loss, Less than Twelve Months |
(66)
|
(95)
|
| Fair Value, Twelve Months or Longer |
19,430
|
42,639
|
| Unrealized Loss, Twelve Months or Longer |
(744)
|
(2,091)
|
| Fair Value |
25,965
|
65,870
|
| Unrealized Loss |
(810)
|
(2,186)
|
| Below investment grade securities: |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
37,713
|
76,452
|
| Unrealized Loss, Less than Twelve Months |
(1,523)
|
(3,822)
|
| Fair Value, Twelve Months or Longer |
317,575
|
295,650
|
| Unrealized Loss, Twelve Months or Longer |
(57,101)
|
(70,205)
|
| Fair Value |
355,288
|
372,102
|
| Unrealized Loss |
(58,624)
|
(74,027)
|
| Below investment grade securities: | Corporates |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
37,713
|
76,452
|
| Unrealized Loss, Less than Twelve Months |
(1,523)
|
(3,822)
|
| Fair Value, Twelve Months or Longer |
317,575
|
293,452
|
| Unrealized Loss, Twelve Months or Longer |
(57,101)
|
(70,205)
|
| Fair Value |
355,288
|
369,904
|
| Unrealized Loss |
(58,624)
|
(74,027)
|
| Below investment grade securities: | Corporates | Industrials |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
15,750
|
54,199
|
| Unrealized Loss, Less than Twelve Months |
(697)
|
(2,656)
|
| Fair Value, Twelve Months or Longer |
185,564
|
142,638
|
| Unrealized Loss, Twelve Months or Longer |
(34,615)
|
(38,350)
|
| Fair Value |
201,314
|
196,837
|
| Unrealized Loss |
(35,312)
|
(41,006)
|
| Below investment grade securities: | Corporates | Financial |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
6,185
|
2,990
|
| Unrealized Loss, Less than Twelve Months |
(32)
|
(53)
|
| Fair Value, Twelve Months or Longer |
96,165
|
126,811
|
| Unrealized Loss, Twelve Months or Longer |
(16,709)
|
(26,171)
|
| Fair Value |
102,350
|
129,801
|
| Unrealized Loss |
(16,741)
|
(26,224)
|
| Below investment grade securities: | Corporates | Utilities |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
15,778
|
19,263
|
| Unrealized Loss, Less than Twelve Months |
(794)
|
(1,113)
|
| Fair Value, Twelve Months or Longer |
35,846
|
24,003
|
| Unrealized Loss, Twelve Months or Longer |
(5,777)
|
(5,684)
|
| Fair Value |
51,624
|
43,266
|
| Unrealized Loss |
(6,571)
|
(6,797)
|
| Below investment grade securities: | Other asset-backed securities |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Fair Value, Less than Twelve Months |
0
|
0
|
| Unrealized Loss, Less than Twelve Months |
0
|
0
|
| Fair Value, Twelve Months or Longer |
0
|
2,198
|
| Unrealized Loss, Twelve Months or Longer |
0
|
0
|
| Fair Value |
0
|
2,198
|
| Unrealized Loss |
$ 0
|
$ 0
|