Investments (Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position) (Details) - USD ($)
$ in Thousands |
Mar. 31, 2024 |
Dec. 31, 2023 |
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
$ 5,763,958
|
$ 1,467,268
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(33,219)
|
(10,821)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
8,290,674
|
8,515,061
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(717,115)
|
(650,461)
|
| Available-for-sale securities, estimated fair value |
14,054,632
|
9,982,329
|
| Available-for-sale securities, gross unrealized holding losses |
(750,334)
|
(661,282)
|
| Short-term investments, estimated fair value, less than 12 months |
2,272,608
|
52,601
|
| Short-term investments, gross unrealized holding losses, less than 12 months |
(1,117)
|
(393)
|
| Short-term investments, estimated fair value, 12 months or longer |
0
|
0
|
| Short-term investments, gross unrealized holding losses, 12 months or longer |
0
|
0
|
| Short-term investments, estimated fair value |
2,272,608
|
52,601
|
| Short-term investments, gross unrealized holding losses |
(1,117)
|
(393)
|
| Fixed maturities, available-for-sale, amortized cost |
15,227,752
|
14,932,286
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
40,835
|
101,335
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(749,217)
|
(660,889)
|
| Available-for-sale fixed maturity investments, estimated fair value |
14,519,370
|
14,372,732
|
| U.S. Treasury securities [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
1,553,613
|
317,027
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(10,383)
|
(2,147)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
1,388,322
|
1,507,784
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(69,025)
|
(60,257)
|
| Available-for-sale securities, estimated fair value |
2,941,935
|
1,824,811
|
| Available-for-sale securities, gross unrealized holding losses |
(79,408)
|
(62,404)
|
| Fixed maturities, available-for-sale, amortized cost |
4,113,319
|
3,811,293
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
12,079
|
35,824
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(79,408)
|
(62,404)
|
| Available-for-sale fixed maturity investments, estimated fair value |
4,045,990
|
3,784,713
|
| U.S. government-sponsored enterprises [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
244,720
|
145,143
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(3,629)
|
(2,134)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
746,832
|
723,537
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(95,801)
|
(87,770)
|
| Available-for-sale securities, estimated fair value |
991,552
|
868,680
|
| Available-for-sale securities, gross unrealized holding losses |
(99,430)
|
(89,904)
|
| Fixed maturities, available-for-sale, amortized cost |
1,289,119
|
1,225,426
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
4,206
|
7,292
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(99,430)
|
(89,904)
|
| Available-for-sale fixed maturity investments, estimated fair value |
1,193,895
|
1,142,814
|
| Obligations of states, municipalities and political subdivisions [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
920,869
|
679,124
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(8,138)
|
(3,881)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
2,376,770
|
2,332,281
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(197,178)
|
(177,697)
|
| Available-for-sale securities, estimated fair value |
3,297,639
|
3,011,405
|
| Available-for-sale securities, gross unrealized holding losses |
(205,316)
|
(181,578)
|
| Fixed maturities, available-for-sale, amortized cost |
4,041,845
|
4,196,096
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
10,059
|
14,787
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(205,316)
|
(181,578)
|
| Available-for-sale fixed maturity investments, estimated fair value |
3,846,588
|
4,029,305
|
| Foreign governments [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
322,098
|
49,056
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(3,059)
|
(128)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
1,079,889
|
1,113,616
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(123,871)
|
(96,746)
|
| Available-for-sale securities, estimated fair value |
1,401,987
|
1,162,672
|
| Available-for-sale securities, gross unrealized holding losses |
(126,930)
|
(96,874)
|
| Fixed maturities, available-for-sale, amortized cost |
1,950,839
|
1,858,845
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
4,132
|
21,450
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(126,930)
|
(96,874)
|
| Available-for-sale fixed maturity investments, estimated fair value |
1,828,041
|
1,783,421
|
| Commercial mortgage-backed securities [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
275,805
|
169,557
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(4,101)
|
(1,792)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
1,722,270
|
1,790,637
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(133,371)
|
(134,561)
|
| Available-for-sale securities, estimated fair value |
1,998,075
|
1,960,194
|
| Available-for-sale securities, gross unrealized holding losses |
(137,472)
|
(136,353)
|
| Fixed maturities, available-for-sale, amortized cost |
2,400,848
|
2,371,406
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
4,780
|
8,605
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(137,472)
|
(136,353)
|
| Available-for-sale fixed maturity investments, estimated fair value |
2,268,156
|
2,243,658
|
| Residential mortgage-backed securities [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
25,905
|
20,420
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(456)
|
(80)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
401,845
|
431,705
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(21,731)
|
(21,781)
|
| Available-for-sale securities, estimated fair value |
427,750
|
452,125
|
| Available-for-sale securities, gross unrealized holding losses |
(22,187)
|
(21,861)
|
| Fixed maturities, available-for-sale, amortized cost |
463,710
|
491,949
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
155
|
334
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(22,187)
|
(21,861)
|
| Available-for-sale fixed maturity investments, estimated fair value |
441,678
|
470,422
|
| Corporate bonds [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
148,340
|
34,340
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(2,336)
|
(266)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
574,746
|
615,501
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(76,138)
|
(71,649)
|
| Available-for-sale securities, estimated fair value |
723,086
|
649,841
|
| Available-for-sale securities, gross unrealized holding losses |
(78,474)
|
(71,915)
|
| Fixed maturities, available-for-sale, amortized cost |
968,072
|
977,271
|
| Available-for-sale fixed maturity investments, gross unrealized holding gains |
5,424
|
13,043
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(78,474)
|
(71,915)
|
| Available-for-sale fixed maturity investments, estimated fair value |
895,022
|
918,399
|
| Total fixed maturities [Member] |
|
|
| Debt Securities, Available-for-sale [Line Items] |
|
|
| Available-for-sale securities, estimated fair value, less than 12 months |
3,491,350
|
1,414,667
|
| Available-for-sale securities, gross unrealized holding losses, less than 12 months |
(32,102)
|
(10,428)
|
| Available-for-sale securities, estimated fair value, 12 months or longer |
8,290,674
|
8,515,061
|
| Available-for-sale securities, gross unrealized holding losses, 12 months or longer |
(717,115)
|
(650,461)
|
| Available-for-sale securities, estimated fair value |
11,782,024
|
9,929,728
|
| Available-for-sale securities, gross unrealized holding losses |
$ (749,217)
|
$ (660,889)
|