SECURITIES (Available for Sale Securities Unrealized Losses) (Details) $ in Thousands	Dec. 31, 2020 USD ($) bankLocation	Dec. 31, 2019 USD ($) bankLocation
Fair Value
Less than 12 months	$ 1,672,530	$ 1,619,266
12 months or longer	508,436	241,232
Total	2,180,966	1,860,498
Unrealized Losses
Less than 12 months	(18,373)	(23,588)
12 months or longer	(5,743)	(4,814)
Total	$ (24,116)	$ (28,402)
Less than 12 Months, Count | bankLocation	127	200
12 Months or Longer, Count | bankLocation	103	58
Total, Count | bankLocation	230	258
U.S. agencies
Fair Value
Less than 12 months	$ 2,981	$ 94,774
12 months or longer	99,922	49,555
Total	102,903	144,329
Unrealized Losses
Less than 12 months	(8)	(957)
12 months or longer	(918)	(604)
Total	$ (926)	$ (1,561)
Less than 12 Months, Count | bankLocation	5	57
12 Months or Longer, Count | bankLocation	72	24
Total, Count | bankLocation	77	81
Obligations of states and political subdivisions
Fair Value
Less than 12 months	$ 346,598	$ 387,534
12 months or longer	0	0
Total	346,598	387,534
Unrealized Losses
Less than 12 months	(2,959)	(9,399)
12 months or longer	0	0
Total	$ (2,959)	$ (9,399)
Less than 12 Months, Count | bankLocation	49	50
12 Months or Longer, Count | bankLocation	0	0
Total, Count | bankLocation	49	50
Mortgage-backed securities - agency
Fair Value
Less than 12 months	$ 653,793	$ 182,614
12 months or longer	31,012	92,928
Total	684,805	275,542
Unrealized Losses
Less than 12 months	(12,342)	(1,763)
12 months or longer	(381)	(2,842)
Total	$ (12,723)	$ (4,605)
Less than 12 Months, Count | bankLocation	35	36
12 Months or Longer, Count | bankLocation	3	17
Total, Count | bankLocation	38	53
Mortgage-backed securities - non-agency
Fair Value
Less than 12 months	$ 378,843	$ 225,807
12 months or longer	1,622	251
Total	380,465	226,058
Unrealized Losses
Less than 12 months	(1,639)	(1,130)
12 months or longer	(1)	0
Total	$ (1,640)	$ (1,130)
Less than 12 Months, Count | bankLocation	17	6
12 Months or Longer, Count | bankLocation	1	1
Total, Count | bankLocation	18	7
Commercial mortgage-backed securities - agency
Fair Value
Less than 12 months	$ 46,541	$ 12,509
12 months or longer	0	1,842
Total	46,541	14,351
Unrealized Losses
Less than 12 months	(738)	(128)
12 months or longer	0	(15)
Total	$ (738)	$ (143)
Less than 12 Months, Count | bankLocation	6	4
12 Months or Longer, Count | bankLocation	0	1
Total, Count | bankLocation	6	5
Commercial mortgage-backed securities - non-agency
Fair Value
Less than 12 months	$ 100,042	$ 214,774
12 months or longer	35,428	55,896
Total	135,470	270,670
Unrealized Losses
Less than 12 months	(15)	(1,544)
12 months or longer	(676)	(439)
Total	$ (691)	$ (1,983)
Less than 12 Months, Count | bankLocation	2	19
12 Months or Longer, Count | bankLocation	3	4
Total, Count | bankLocation	5	23
Asset-backed securities
Fair Value
Less than 12 months	$ 141,824	$ 501,254
12 months or longer	340,452	40,760
Total	482,276	542,014
Unrealized Losses
Less than 12 months	(643)	(8,667)
12 months or longer	(3,767)	(914)
Total	$ (4,410)	$ (9,581)
Less than 12 Months, Count | bankLocation	9	28
12 Months or Longer, Count | bankLocation	24	11
Total, Count | bankLocation	33	39
Corporate bonds
Fair Value
Less than 12 months	$ 1,908	$ 0
12 months or longer	0	0
Total	1,908	0
Unrealized Losses
Less than 12 months	(29)	0
12 months or longer	0	0
Total	$ (29)	$ 0
Less than 12 Months, Count | bankLocation	4
12 Months or Longer, Count | bankLocation	0	0
Total, Count | bankLocation	4	0