INVESTMENTS - Age of Gross Unrealized Losses and Associated Fair Value by Investment Category (Details) - USD ($)
$ in Thousands |
Sep. 30, 2023 |
Dec. 31, 2022 |
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
$ 254,082
|
$ 1,502,821
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
13,943
|
89,206
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
2,746,020
|
1,785,690
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
468,264
|
329,398
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
3,000,102
|
3,288,511
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(482,207)
|
(418,604)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
4,656
|
36,214
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
(231)
|
(3,422)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
63,640
|
37,399
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
(11,177)
|
(4,219)
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
68,296
|
73,613
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
(11,408)
|
(7,641)
|
| U.S. Treasuries |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
2,146
|
2,383
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
40
|
46
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
29,996
|
30,313
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
4,903
|
4,570
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
32,142
|
32,696
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(4,943)
|
(4,616)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
0
|
0
|
| Securities of U.S. government agencies and corporations |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
0
|
0
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
0
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
66,125
|
66,468
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
15,309
|
13,914
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
66,125
|
66,468
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(15,309)
|
(13,914)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
0
|
0
|
| Residential Mortgage Backed Securities [Member] |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
77,097
|
195,972
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
4,853
|
10,413
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
507,386
|
443,415
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
116,345
|
87,049
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
584,483
|
639,387
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(121,198)
|
(97,462)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
0
|
0
|
| Commercial Mortgage Backed Securities [Member] |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
14,712
|
440,207
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
650
|
18,823
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
533,334
|
175,530
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
49,749
|
28,551
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
548,046
|
615,737
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(50,399)
|
(47,374)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
17,656
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
(2,197)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
27,441
|
13,593
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
(5,958)
|
(1,917)
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
27,441
|
31,249
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
(5,958)
|
(4,114)
|
| Collateralized Mortgage Backed Securities [Member] |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
26,373
|
199,138
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
1,091
|
12,453
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
386,540
|
269,242
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
74,568
|
48,986
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
412,913
|
468,380
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(75,659)
|
(61,439)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
6,317
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
(606)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
7,228
|
2,136
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
(1,182)
|
(221)
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
7,228
|
8,453
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
(1,182)
|
(827)
|
| Obligations of state and other political subdivisions |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
95,647
|
295,913
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
6,574
|
31,196
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
530,379
|
368,673
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
144,824
|
92,972
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
626,026
|
664,586
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(151,398)
|
(124,168)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
4,656
|
5,160
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
(231)
|
(201)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
1,459
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
(299)
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
6,115
|
5,160
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
(530)
|
(201)
|
| Asset-backed Securities [Member] |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
28,394
|
250,946
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
448
|
9,410
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
578,706
|
422,090
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
49,231
|
51,565
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
607,100
|
673,036
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(49,679)
|
(60,975)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
0
|
0
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
0
|
0
|
| Other securities |
|
|
| Investments, Unrealized Loss Position [Line Items] |
|
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months |
9,713
|
118,262
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
287
|
6,865
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer |
113,554
|
9,959
|
| Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
13,335
|
1,791
|
| Debt Securities, Available-for-Sale, Unrealized Loss Position |
123,267
|
128,221
|
| Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax |
(13,622)
|
(8,656)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value |
0
|
7,081
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss |
0
|
(418)
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value |
27,512
|
21,670
|
| Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss |
(3,738)
|
(2,081)
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value |
27,512
|
28,751
|
| Debt Securities, Held-to-Maturity, Unrealized Loss Position, Accumulated Loss |
$ (3,738)
|
$ (2,499)
|