INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Estimated Fair Value
Less than 12 months, estimated fair value	$ 1,238,635	$ 6,826
12 months or more, estimated fair value	3,392	3,953
Total estimated fair value	1,242,027	10,779
Unrealized Losses
Less than 12 months, unrealized losses	(63,980)	(12)
12 months or more, unrealized losses	(267)	(183)
Total unrealized losses	(64,247)	(195)
U.S. Treasuries
Estimated Fair Value
Less than 12 months, estimated fair value	503,810
12 months or more, estimated fair value	0
Total estimated fair value	503,810
Unrealized Losses
Less than 12 months, unrealized losses	(16,275)
12 months or more, unrealized losses	0
Total unrealized losses	(16,275)
U.S. government-sponsored agencies
Estimated Fair Value
Less than 12 months, estimated fair value	977
12 months or more, estimated fair value	0
Total estimated fair value	977
Unrealized Losses
Less than 12 months, unrealized losses	(62)
12 months or more, unrealized losses	0
Total unrealized losses	(62)
State, county and municipal securities
Estimated Fair Value
Less than 12 months, estimated fair value	30,049
12 months or more, estimated fair value	0
Total estimated fair value	30,049
Unrealized Losses
Less than 12 months, unrealized losses	(1,584)
12 months or more, unrealized losses	0
Total unrealized losses	(1,584)
Corporate debt securities
Estimated Fair Value
Less than 12 months, estimated fair value	12,596	0
12 months or more, estimated fair value	1,200	1,380
Total estimated fair value	13,796	1,380
Unrealized Losses
Less than 12 months, unrealized losses	(301)	0
12 months or more, unrealized losses	(221)	(120)
Total unrealized losses	(522)	(120)
SBA pool securities
Estimated Fair Value
Less than 12 months, estimated fair value	26,326	1,312
12 months or more, estimated fair value	2,191	2,572
Total estimated fair value	28,517	3,884
Unrealized Losses
Less than 12 months, unrealized losses	(2,170)	(6)
12 months or more, unrealized losses	(46)	(63)
Total unrealized losses	(2,216)	(69)
Mortgage-backed securities
Estimated Fair Value
Less than 12 months, estimated fair value	664,877	5,514
12 months or more, estimated fair value	1	1
Total estimated fair value	664,878	5,515
Unrealized Losses
Less than 12 months, unrealized losses	(43,588)	(6)
12 months or more, unrealized losses	0	0
Total unrealized losses	$ (43,588)	$ (6)