Investments in Fixed Maturity Securities (Investments in fixed maturity securities) (Details) - USD ($)
$ in Thousands |
Jun. 30, 2026 |
Mar. 31, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total held to maturity, Amortized Cost |
$ 15,983
|
|
$ 30,615
|
|
|
|
| Held-to-maturity, Allowance for Credit Loss |
0
|
$ 0
|
(9)
|
$ (14)
|
$ (20)
|
$ (25)
|
| Held to maturity, Gross Unrealized Gains |
436
|
|
872
|
|
|
|
| Held to maturity, Gross Unrealized Losses |
0
|
|
0
|
|
|
|
| Total held to maturity, Fair Value |
16,419
|
|
31,478
|
|
|
|
| Carrying Value |
15,983
|
|
30,606
|
|
|
|
| Total available for sale, Amortized Cost |
26,249,654
|
|
25,139,753
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
(440)
|
(306)
|
(65)
|
(318)
|
(333)
|
(646)
|
| Total available for sale, Gross Unrealized Gains |
152,033
|
|
321,700
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(517,238)
|
|
(444,332)
|
|
|
|
| Total available for sale, Fair Value |
25,884,009
|
|
25,017,056
|
|
|
|
| Total fixed maturity securities available for sale |
25,884,009
|
|
25,017,056
|
|
|
|
| Fixed maturity securities, amortized cost |
26,265,637
|
|
25,170,368
|
|
|
|
| Fixed maturity securities, allowance for credit loss |
(440)
|
|
(74)
|
|
|
|
| Total investments in fixed maturity securities, Gross Unrealized Gains |
152,469
|
|
322,572
|
|
|
|
| Total investments in fixed maturity securities, Gross Unrealized Losses |
(517,238)
|
|
(444,332)
|
|
|
|
| Total investments in fixed maturity securities, Fair Value |
25,900,428
|
|
25,048,534
|
|
|
|
| Total investments in fixed maturity securities, Carrying Value |
25,899,992
|
|
25,047,662
|
|
|
|
| State and municipal |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total held to maturity, Amortized Cost |
14,363
|
|
28,777
|
|
|
|
| Held-to-maturity, Allowance for Credit Loss |
0
|
|
(9)
|
|
|
|
| Held to maturity, Gross Unrealized Gains |
397
|
|
796
|
|
|
|
| Held to maturity, Gross Unrealized Losses |
0
|
|
0
|
|
|
|
| Total held to maturity, Fair Value |
14,760
|
|
29,564
|
|
|
|
| Carrying Value |
14,363
|
|
28,768
|
|
|
|
| Total available for sale, Amortized Cost |
1,673,017
|
|
1,862,104
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
0
|
0
|
0
|
(10)
|
0
|
| Total available for sale, Gross Unrealized Gains |
6,776
|
|
13,503
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(37,437)
|
|
(38,413)
|
|
|
|
| Total available for sale, Fair Value |
1,642,356
|
|
1,837,194
|
|
|
|
| Total fixed maturity securities available for sale |
1,642,356
|
|
1,837,194
|
|
|
|
| Residential mortgage-backed |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total held to maturity, Amortized Cost |
1,620
|
|
1,838
|
|
|
|
| Held-to-maturity, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Held to maturity, Gross Unrealized Gains |
39
|
|
76
|
|
|
|
| Held to maturity, Gross Unrealized Losses |
0
|
|
0
|
|
|
|
| Total held to maturity, Fair Value |
1,659
|
|
1,914
|
|
|
|
| Carrying Value |
1,620
|
|
1,838
|
|
|
|
| Total available for sale, Amortized Cost |
4,388,433
|
|
4,584,970
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
(84)
|
|
(65)
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
32,329
|
|
71,048
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(143,610)
|
|
(132,645)
|
|
|
|
| Total available for sale, Fair Value |
4,277,068
|
|
4,523,308
|
|
|
|
| Total fixed maturity securities available for sale |
4,277,068
|
|
4,523,308
|
|
|
|
| U.S. government and government agency |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
4,427,552
|
|
3,964,375
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
20,690
|
|
48,820
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(45,246)
|
|
(15,157)
|
|
|
|
| Total available for sale, Fair Value |
4,402,996
|
|
3,998,038
|
|
|
|
| Total fixed maturity securities available for sale |
4,402,996
|
|
3,998,038
|
|
|
|
| Special revenue |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
1,047,316
|
|
1,206,387
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
3,294
|
|
6,002
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(25,253)
|
|
(27,943)
|
|
|
|
| Total available for sale, Fair Value |
1,025,357
|
|
1,184,446
|
|
|
|
| Total fixed maturity securities available for sale |
1,025,357
|
|
1,184,446
|
|
|
|
| State general obligation |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
200,210
|
|
203,543
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
1,545
|
|
3,465
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(4,165)
|
|
(3,848)
|
|
|
|
| Total available for sale, Fair Value |
197,590
|
|
203,160
|
|
|
|
| Total fixed maturity securities available for sale |
197,590
|
|
203,160
|
|
|
|
| Pre-refunded |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
105,873
|
|
74,276
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
338
|
|
619
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(1,650)
|
|
(111)
|
|
|
|
| Total available for sale, Fair Value |
104,561
|
|
74,784
|
|
|
|
| Total fixed maturity securities available for sale |
104,561
|
|
74,784
|
|
|
|
| Corporate backed |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
135,432
|
|
159,876
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
915
|
|
1,958
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(3,099)
|
|
(3,459)
|
|
|
|
| Total available for sale, Fair Value |
133,248
|
|
158,375
|
|
|
|
| Total fixed maturity securities available for sale |
133,248
|
|
158,375
|
|
|
|
| Local general obligation |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
184,186
|
|
218,022
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
684
|
|
1,459
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(3,270)
|
|
(3,052)
|
|
|
|
| Total available for sale, Fair Value |
181,600
|
|
216,429
|
|
|
|
| Total fixed maturity securities available for sale |
181,600
|
|
216,429
|
|
|
|
| Commercial |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
204,907
|
|
281,573
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
2,032
|
|
3,632
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(155)
|
|
(35)
|
|
|
|
| Total available for sale, Fair Value |
206,784
|
|
285,170
|
|
|
|
| Total fixed maturity securities available for sale |
206,784
|
|
285,170
|
|
|
|
| Mortgage-backed |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
4,593,340
|
|
4,866,543
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
(84)
|
(77)
|
(65)
|
0
|
0
|
(430)
|
| Total available for sale, Gross Unrealized Gains |
34,361
|
|
74,680
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(143,765)
|
|
(132,680)
|
|
|
|
| Total available for sale, Fair Value |
4,483,852
|
|
4,808,478
|
|
|
|
| Total fixed maturity securities available for sale |
4,483,852
|
|
4,808,478
|
|
|
|
| Asset-backed |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
4,090,646
|
|
3,807,393
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
(356)
|
(229)
|
0
|
0
|
0
|
0
|
| Total available for sale, Gross Unrealized Gains |
8,365
|
|
20,196
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(22,127)
|
|
(17,243)
|
|
|
|
| Total available for sale, Fair Value |
4,076,528
|
|
3,810,346
|
|
|
|
| Total fixed maturity securities available for sale |
4,076,528
|
|
3,810,346
|
|
|
|
| Industrial |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
3,754,054
|
|
3,627,567
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
26,731
|
|
57,466
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(37,844)
|
|
(36,499)
|
|
|
|
| Total available for sale, Fair Value |
3,742,941
|
|
3,648,534
|
|
|
|
| Total fixed maturity securities available for sale |
3,742,941
|
|
3,648,534
|
|
|
|
| Financial |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
3,644,516
|
|
3,438,348
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
25,526
|
|
61,180
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(23,056)
|
|
(16,460)
|
|
|
|
| Total available for sale, Fair Value |
3,646,986
|
|
3,483,068
|
|
|
|
| Total fixed maturity securities available for sale |
3,646,986
|
|
3,483,068
|
|
|
|
| Utilities |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
1,700,715
|
|
1,300,506
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
8,980
|
|
22,593
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(16,749)
|
|
(8,878)
|
|
|
|
| Total available for sale, Fair Value |
1,692,946
|
|
1,314,221
|
|
|
|
| Total fixed maturity securities available for sale |
1,692,946
|
|
1,314,221
|
|
|
|
| Other |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
194,685
|
|
240,374
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
1,183
|
|
2,356
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(646)
|
|
(1,142)
|
|
|
|
| Total available for sale, Fair Value |
195,222
|
|
241,588
|
|
|
|
| Total fixed maturity securities available for sale |
195,222
|
|
241,588
|
|
|
|
| Corporate |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
9,293,970
|
|
8,606,795
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
|
0
|
|
|
|
| Total available for sale, Gross Unrealized Gains |
62,420
|
|
143,595
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(78,295)
|
|
(62,979)
|
|
|
|
| Total available for sale, Fair Value |
9,278,095
|
|
8,687,411
|
|
|
|
| Total fixed maturity securities available for sale |
9,278,095
|
|
8,687,411
|
|
|
|
| Foreign government |
|
|
|
|
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
|
|
|
|
| Total available for sale, Amortized Cost |
2,171,129
|
|
2,032,543
|
|
|
|
| Available-for-sale, Allowance for Credit Loss |
0
|
$ 0
|
0
|
$ (318)
|
$ (323)
|
$ (216)
|
| Total available for sale, Gross Unrealized Gains |
19,421
|
|
20,906
|
|
|
|
| Total available for sale, Gross Unrealized Losses |
(190,368)
|
|
(177,860)
|
|
|
|
| Total available for sale, Fair Value |
2,000,182
|
|
1,875,589
|
|
|
|
| Total fixed maturity securities available for sale |
$ 2,000,182
|
|
$ 1,875,589
|
|
|
|