DEBT SECURITIES - Schedule of Debt Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value
Less than 12 months	$ 13,033	$ 1,070,674
12 months or more	2,049,784	1,368,859
Total	2,062,817	2,439,533
Unrealized Losses
Less than 12 months	(65)	(81,841)
12 months or more	(247,180)	(229,363)
Total	(247,245)	(311,204)
Fair Value
Less than 12 months		58,065
12 months or more	730,397	727,230
Total	730,397	785,295
Unrealized Losses
Less than 12 months		(8,009)
12 months or more	(142,231)	(125,008)
Total	(142,231)	(133,017)
U.S. Treasury securities
Fair Value
Less than 12 months	0	74
12 months or more	15,946	113,987
Total	15,946	114,061
Unrealized Losses
Less than 12 months	0	0
12 months or more	(85)	(3,744)
Total	(85)	(3,744)
Obligations of U.S. government corporations and agencies
Fair Value
Less than 12 months	0	19,603
12 months or more	5,709	0
Total	5,709	19,603
Unrealized Losses
Less than 12 months	0	(321)
12 months or more	(58)	0
Total	(58)	(321)
Obligations of states and political subdivisions
Fair Value
Less than 12 months	11,442	166,147
12 months or more	146,797	75,217
Total	158,239	241,364
Unrealized Losses
Less than 12 months	(54)	(10,059)
12 months or more	(17,972)	(16,016)
Total	(18,026)	(26,075)
Asset-backed securities
Fair Value
Less than 12 months	0	390,164
12 months or more	468,223	79,711
Total	468,223	469,875
Unrealized Losses
Less than 12 months	0	(15,648)
12 months or more	(1,823)	(4,035)
Total	(1,823)	(19,683)
Commercial mortgage-backed securities
Fair Value
Less than 12 months	0	89,428
12 months or more	103,509	18,966
Total	103,509	108,394
Unrealized Losses
Less than 12 months	0	(12,623)
12 months or more	(15,535)	(3,406)
Total	(15,535)	(16,029)
Fair Value
Less than 12 months		58,065
12 months or more	357,526	353,017
Total	357,526	411,082
Unrealized Losses
Less than 12 months		(8,009)
12 months or more	(71,000)	(55,729)
Total	(71,000)	(63,738)
Residential mortgage-backed securities
Fair Value
Less than 12 months	141	366,221
12 months or more	1,110,906	876,668
Total	1,111,047	1,242,889
Unrealized Losses
Less than 12 months	(1)	(38,111)
12 months or more	(195,546)	(182,606)
Total	(195,547)	(220,717)
Fair Value
Less than 12 months		0
12 months or more	372,871	374,213
Total	372,871	374,213
Unrealized Losses
Less than 12 months		0
12 months or more	(71,231)	(69,279)
Total	(71,231)	(69,279)
Corporate debt securities
Fair Value
Less than 12 months	1,450	39,037
12 months or more	198,694	204,310
Total	200,144	243,347
Unrealized Losses
Less than 12 months	(10)	(5,079)
12 months or more	(16,161)	(19,556)
Total	$ (16,171)	$ (24,635)