SECURITIES (Debt securities available for sale) (Details) $ in Thousands	Jun. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 542,086	$ 2,259,415
Unrealized Losses, Less than 12 months	$ (40,050)	$ (147,396)
Count, Less than 12 months | security	60	243
Fair Value, 12 months or longer	$ 4,552,435	$ 3,037,801
Unrealized Losses, 12 months or longer	$ (577,592)	$ (495,684)
Count, 12 months or longer | security	454	284
Fair Value, Total	$ 5,094,521	$ 5,297,216
Unrealized Losses, Total	$ (617,642)	$ (643,080)
Count, Total | security	514	527
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 28,270	$ 28,699
Unrealized Losses, Less than 12 months	$ (652)	$ (678)
Count, Less than 12 months | security	5	4
Fair Value, 12 months or longer	$ 3,409	$ 0
Unrealized Losses, 12 months or longer	$ (82)	$ 0
Count, 12 months or longer | security	1	0
Fair Value, Total	$ 31,679	$ 28,699
Unrealized Losses, Total	$ (734)	$ (678)
Count, Total | security	6	4
U.S. agencies
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 0	$ 16,487
Unrealized Losses, Less than 12 months	$ 0	$ (222)
Count, Less than 12 months | security	0	5
Fair Value, 12 months or longer	$ 43,036	$ 26,648
Unrealized Losses, 12 months or longer	$ (5,908)	$ (6,080)
Count, 12 months or longer | security	6	2
Fair Value, Total	$ 43,036	$ 43,135
Unrealized Losses, Total	$ (5,908)	$ (6,302)
Count, Total | security	6	7
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 2,698	$ 288,457
Unrealized Losses, Less than 12 months	$ (118)	$ (28,378)
Count, Less than 12 months | security	3	69
Fair Value, 12 months or longer	$ 844,628	$ 589,641
Unrealized Losses, 12 months or longer	$ (136,035)	$ (141,777)
Count, 12 months or longer | security	162	113
Fair Value, Total	$ 847,326	$ 878,098
Unrealized Losses, Total	$ (136,153)	$ (170,155)
Count, Total | security	165	182
Mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 27,450	$ 241,288
Unrealized Losses, Less than 12 months	$ (1,774)	$ (21,420)
Count, Less than 12 months | security	30	99
Fair Value, 12 months or longer	$ 1,657,307	$ 1,528,951
Unrealized Losses, 12 months or longer	$ (269,788)	$ (248,623)
Count, 12 months or longer | security	191	126
Fair Value, Total	$ 1,684,757	$ 1,770,239
Unrealized Losses, Total	$ (271,562)	$ (270,043)
Count, Total | security	221	225
Mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 393,712	$ 950,054
Unrealized Losses, Less than 12 months	$ (33,619)	$ (70,213)
Count, Less than 12 months | security	16	25
Fair Value, 12 months or longer	$ 1,205,116	$ 693,531
Unrealized Losses, 12 months or longer	$ (121,158)	$ (76,636)
Count, 12 months or longer | security	43	25
Fair Value, Total	$ 1,598,828	$ 1,643,585
Unrealized Losses, Total	$ (154,777)	$ (146,849)
Count, Total | security	59	50
Commercial mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 1,795	$ 27,732
Unrealized Losses, Less than 12 months	$ (96)	$ (2,291)
Count, Less than 12 months | security	1	12
Fair Value, 12 months or longer	$ 82,030	$ 57,392
Unrealized Losses, 12 months or longer	$ (15,151)	$ (13,104)
Count, 12 months or longer | security	19	7
Fair Value, Total	$ 83,825	$ 85,124
Unrealized Losses, Total	$ (15,247)	$ (15,395)
Count, Total | security	20	19
Commercial mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 7,254	$ 530,541
Unrealized Losses, Less than 12 months	$ (262)	$ (16,830)
Count, Less than 12 months | security	2	15
Fair Value, 12 months or longer	$ 588,183	$ 84,619
Unrealized Losses, 12 months or longer	$ (17,295)	$ (3,222)
Count, 12 months or longer | security	16	4
Fair Value, Total	$ 595,437	$ 615,160
Unrealized Losses, Total	$ (17,557)	$ (20,052)
Count, Total | security	18	19
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 31,941	$ 118,613
Unrealized Losses, Less than 12 months	$ (1,997)	$ (6,107)
Count, Less than 12 months | security	1	7
Fair Value, 12 months or longer	$ 121,281	$ 56,621
Unrealized Losses, 12 months or longer	$ (10,919)	$ (6,236)
Count, 12 months or longer | security	10	6
Fair Value, Total	$ 153,222	$ 175,234
Unrealized Losses, Total	$ (12,916)	$ (12,343)
Count, Total | security	11	13
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 48,966	$ 57,544
Unrealized Losses, Less than 12 months	$ (1,532)	$ (1,257)
Count, Less than 12 months | security	2	7
Fair Value, 12 months or longer	$ 7,445	$ 398
Unrealized Losses, 12 months or longer	$ (1,256)	$ (6)
Count, 12 months or longer | security	6	1
Fair Value, Total	$ 56,411	$ 57,942
Unrealized Losses, Total	$ (2,788)	$ (1,263)
Count, Total | security	8	8