SECURITIES (Debt securities available for sale) (Details) $ in Thousands	Sep. 30, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 3,394,796	$ 3,226,422
Unrealized Losses, Less than 12 months	$ (351,527)	$ (57,123)
Count, Less than 12 months | security	377	242
Fair Value, 12 months or longer	$ 2,017,243	$ 815,822
Unrealized Losses, 12 months or longer	$ (330,742)	$ (27,110)
Count, 12 months or longer | security	158	86
Fair Value, Total	$ 5,412,039	$ 4,042,244
Unrealized Losses, Total	$ (682,269)	$ (84,233)
Count, Total | security	535	328
U.S. agencies
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 27,662	$ 100,839
Unrealized Losses, Less than 12 months	$ (2,398)	$ (812)
Count, Less than 12 months | security	6	2
Fair Value, 12 months or longer	$ 15,638	$ 0
Unrealized Losses, 12 months or longer	$ (3,906)	$ 0
Count, 12 months or longer | security	1	0
Fair Value, Total	$ 43,300	$ 100,839
Unrealized Losses, Total	$ (6,304)	$ (812)
Count, Total | security	7	2
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 703,542	$ 596,866
Unrealized Losses, Less than 12 months	$ (175,773)	$ (10,115)
Count, Less than 12 months | security	141	113
Fair Value, 12 months or longer	$ 127,428	$ 236,329
Unrealized Losses, 12 months or longer	$ (42,565)	$ (6,501)
Count, 12 months or longer | security	41	49
Fair Value, Total	$ 830,970	$ 833,195
Unrealized Losses, Total	$ (218,338)	$ (16,616)
Count, Total | security	182	162
Mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 523,192	$ 1,383,808
Unrealized Losses, Less than 12 months	$ (53,036)	$ (33,291)
Count, Less than 12 months | security	143	83
Fair Value, 12 months or longer	$ 1,303,192	$ 474,724
Unrealized Losses, 12 months or longer	$ (216,041)	$ (17,891)
Count, 12 months or longer | security	82	19
Fair Value, Total	$ 1,826,384	$ 1,858,532
Unrealized Losses, Total	$ (269,077)	$ (51,182)
Count, Total | security	225	102
Mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 1,317,914	$ 929,515
Unrealized Losses, Less than 12 months	$ (93,124)	$ (10,870)
Count, Less than 12 months | security	35	27
Fair Value, 12 months or longer	$ 394,034	$ 23,821
Unrealized Losses, 12 months or longer	$ (47,752)	$ (159)
Count, 12 months or longer | security	16	5
Fair Value, Total	$ 1,711,948	$ 953,336
Unrealized Losses, Total	$ (140,876)	$ (11,029)
Count, Total | security	51	32
Commercial mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 30,467	$ 26,999
Unrealized Losses, Less than 12 months	$ (2,733)	$ (689)
Count, Less than 12 months | security	14	8
Fair Value, 12 months or longer	$ 55,681	$ 53,025
Unrealized Losses, 12 months or longer	$ (13,408)	$ (2,225)
Count, 12 months or longer | security	11	5
Fair Value, Total	$ 86,148	$ 80,024
Unrealized Losses, Total	$ (16,141)	$ (2,914)
Count, Total | security	25	13
Commercial mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 626,025	$ 74,450
Unrealized Losses, Less than 12 months	$ (18,189)	$ (145)
Count, Less than 12 months | security	19	3
Fair Value, 12 months or longer	$ 63,650	$ 14,124
Unrealized Losses, 12 months or longer	$ (899)	$ (218)
Count, 12 months or longer | security	2	2
Fair Value, Total	$ 689,675	$ 88,574
Unrealized Losses, Total	$ (19,088)	$ (363)
Count, Total | security	21	5
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 130,835	$ 113,945
Unrealized Losses, Less than 12 months	$ (4,860)	$ (1,201)
Count, Less than 12 months | security	8	6
Fair Value, 12 months or longer	$ 57,620	$ 13,799
Unrealized Losses, 12 months or longer	$ (6,171)	$ (116)
Count, 12 months or longer | security	5	6
Fair Value, Total	$ 188,455	$ 127,744
Unrealized Losses, Total	$ (11,031)	$ (1,317)
Count, Total | security	13	12
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 8,422
Unrealized Losses, Less than 12 months	$ (787)
Count, Less than 12 months | security	7
Fair Value, 12 months or longer	$ 0
Unrealized Losses, 12 months or longer	$ 0
Count, 12 months or longer | security	0
Fair Value, Total	$ 8,422
Unrealized Losses, Total	$ (787)
Count, Total | security	7
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 months	$ 26,737
Unrealized Losses, Less than 12 months	$ (627)
Count, Less than 12 months | security	4
Fair Value, 12 months or longer	$ 0
Unrealized Losses, 12 months or longer	$ 0
Count, 12 months or longer | security	0
Fair Value, Total	$ 26,737
Unrealized Losses, Total	$ (627)
Count, Total | security	4