Investments - Schedule of Fixed Maturity Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands |
Jun. 30, 2025
USD ($)
security
|
Dec. 31, 2024
USD ($)
security
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 809,616
|
$ 1,444,660
|
Less than 12 months, Gross unrealized losses |
$ (16,544)
|
$ (34,364)
|
Less than 12 months, Number of securities | security |
264
|
544
|
12 months or more, Fair value |
$ 2,148,648
|
$ 2,722,049
|
12 months or more, Gross unrealized losses |
$ (158,343)
|
$ (238,076)
|
12 months or more, Number of securities | security |
426
|
566
|
Fair value |
$ 2,958,264
|
$ 4,166,709
|
Gross unrealized losses |
$ (174,887)
|
$ (272,440)
|
Number of securities | security |
690
|
1,110
|
U.S. government, agencies and GSEs |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 69,908
|
$ 157,596
|
Less than 12 months, Gross unrealized losses |
$ (1,670)
|
$ (4,704)
|
Less than 12 months, Number of securities | security |
13
|
32
|
12 months or more, Fair value |
$ 18,086
|
$ 19,998
|
12 months or more, Gross unrealized losses |
$ (196)
|
$ (381)
|
12 months or more, Number of securities | security |
6
|
9
|
Fair value |
$ 87,994
|
$ 177,594
|
Gross unrealized losses |
$ (1,866)
|
$ (5,085)
|
Number of securities | security |
19
|
41
|
State and political subdivisions |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 65,525
|
$ 48,280
|
Less than 12 months, Gross unrealized losses |
$ (5,002)
|
$ (2,366)
|
Less than 12 months, Number of securities | security |
21
|
17
|
12 months or more, Fair value |
$ 383,015
|
$ 396,638
|
12 months or more, Gross unrealized losses |
$ (56,093)
|
$ (73,261)
|
12 months or more, Number of securities | security |
76
|
84
|
Fair value |
$ 448,540
|
$ 444,918
|
Gross unrealized losses |
$ (61,095)
|
$ (75,627)
|
Number of securities | security |
97
|
101
|
Non-U.S. government |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 16,110
|
$ 56,631
|
Less than 12 months, Gross unrealized losses |
$ (211)
|
$ (1,236)
|
Less than 12 months, Number of securities | security |
24
|
76
|
12 months or more, Fair value |
$ 9,836
|
$ 9,692
|
12 months or more, Gross unrealized losses |
$ (404)
|
$ (622)
|
12 months or more, Number of securities | security |
1
|
1
|
Fair value |
$ 25,946
|
$ 66,323
|
Gross unrealized losses |
$ (615)
|
$ (1,858)
|
Number of securities | security |
25
|
77
|
U.S. corporate |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 392,199
|
$ 881,643
|
Less than 12 months, Gross unrealized losses |
$ (6,967)
|
$ (20,844)
|
Less than 12 months, Number of securities | security |
95
|
265
|
12 months or more, Fair value |
$ 1,043,840
|
$ 1,379,860
|
12 months or more, Gross unrealized losses |
$ (67,274)
|
$ (108,740)
|
12 months or more, Number of securities | security |
186
|
264
|
Fair value |
$ 1,436,039
|
$ 2,261,503
|
Gross unrealized losses |
$ (74,241)
|
$ (129,584)
|
Number of securities | security |
281
|
529
|
Non-U.S. corporate |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 84,807
|
$ 195,648
|
Less than 12 months, Gross unrealized losses |
$ (1,500)
|
$ (4,015)
|
Less than 12 months, Number of securities | security |
33
|
102
|
12 months or more, Fair value |
$ 270,004
|
$ 385,508
|
12 months or more, Gross unrealized losses |
$ (15,133)
|
$ (26,035)
|
12 months or more, Number of securities | security |
52
|
74
|
Fair value |
$ 354,811
|
$ 581,156
|
Gross unrealized losses |
$ (16,633)
|
$ (30,050)
|
Number of securities | security |
85
|
176
|
Residential mortgage-backed |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 100,554
|
$ 3,313
|
Less than 12 months, Gross unrealized losses |
$ (559)
|
$ (31)
|
Less than 12 months, Number of securities | security |
32
|
3
|
12 months or more, Fair value |
$ 0
|
$ 2,822
|
12 months or more, Gross unrealized losses |
$ 0
|
$ (26)
|
12 months or more, Number of securities | security |
0
|
4
|
Fair value |
$ 100,554
|
$ 6,135
|
Gross unrealized losses |
$ (559)
|
$ (57)
|
Number of securities | security |
32
|
7
|
Other asset-backed |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 77,194
|
$ 101,549
|
Less than 12 months, Gross unrealized losses |
$ (632)
|
$ (1,168)
|
Less than 12 months, Number of securities | security |
43
|
49
|
12 months or more, Fair value |
$ 423,867
|
$ 527,531
|
12 months or more, Gross unrealized losses |
$ (19,243)
|
$ (29,011)
|
12 months or more, Number of securities | security |
105
|
130
|
Fair value |
$ 501,061
|
$ 629,080
|
Gross unrealized losses |
$ (19,875)
|
$ (30,179)
|
Number of securities | security |
148
|
179
|
Commercial mortgage-backed |
|
|
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |
|
|
Less than 12 months, Fair value |
$ 3,319
|
|
Less than 12 months, Gross unrealized losses |
$ (3)
|
|
Less than 12 months, Number of securities | security |
3
|
|
12 months or more, Fair value |
$ 0
|
|
12 months or more, Gross unrealized losses |
$ 0
|
|
12 months or more, Number of securities | security |
0
|
|
Fair value |
$ 3,319
|
|
Gross unrealized losses |
$ (3)
|
|
Number of securities | security |
3
|
|