SEGMENT REPORTING - Schedule of Segment Reporting, by Reportable Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Interest income	$ 202,568	$ 173,751	$ 385,942	$ 351,701
Interest expense	11,204	11,899	22,034	24,872
Net interest income	191,364	161,852	363,908	326,829
Provision for credit losses	14,924	142	21,155	(28,449)
Noninterest income	83,841	89,240	170,752	207,213
Noninterest expense
Salaries and employee benefits	81,545	85,505	165,826	181,490
Occupancy and equipment	12,746	10,812	25,473	22,593
Data processing and communications expenses	12,155	11,877	24,727	23,761
Other expenses	35,750	27,567	69,990	56,715
Total noninterest expense	142,196	135,761	286,016	284,559
Income before income tax expense	118,085	115,189	227,489	277,932
Income tax expense	28,019	26,862	55,725	64,643
Net income	90,066	88,327	171,764	213,289
Total assets	23,687,470	21,886,931	23,687,470	21,886,931	$ 23,858,321
Goodwill	1,023,056	928,005	1,023,056	928,005	1,012,620
Other intangible assets, net	115,613	63,783	115,613	63,783	$ 125,938
Banking Division
Segment Reporting Information [Line Items]
Interest income	141,844	109,260	271,134	221,639
Interest expense	(10,278)	(1,410)	(14,733)	(1,847)
Net interest income	152,122	110,670	285,867	223,486
Provision for credit losses	10,175	(3,949)	15,401	(27,853)
Noninterest income	23,469	16,171	44,833	32,909
Noninterest expense
Salaries and employee benefits	46,733	37,814	95,928	80,537
Occupancy and equipment	11,168	9,050	22,242	19,170
Data processing and communications expenses	10,863	10,280	22,093	20,481
Other expenses	21,123	18,763	41,168	38,473
Total noninterest expense	89,887	75,907	181,431	158,661
Income before income tax expense	75,529	54,883	133,868	125,587
Income tax expense	19,120	14,196	36,116	32,652
Net income	56,409	40,687	97,752	92,935
Total assets	17,009,855	15,561,628	17,009,855	15,561,628
Goodwill	958,558	863,507	958,558	863,507
Other intangible assets, net	105,198	50,418	105,198	50,418
Retail Mortgage Division
Segment Reporting Information [Line Items]
Interest income	38,055	34,085	70,887	64,284
Interest expense	17,276	11,552	30,813	22,767
Net interest income	20,779	22,533	40,074	41,517
Provision for credit losses	4,499	5,647	6,086	1,094
Noninterest income	57,795	69,055	119,444	166,695
Noninterest expense
Salaries and employee benefits	31,219	44,798	62,833	94,636
Occupancy and equipment	1,406	1,553	2,877	3,029
Data processing and communications expenses	1,123	1,435	2,295	2,981
Other expenses	12,812	7,638	25,457	15,827
Total noninterest expense	46,560	55,424	93,462	116,473
Income before income tax expense	27,515	30,517	59,970	90,645
Income tax expense	5,779	6,408	12,594	19,035
Net income	21,736	24,109	47,376	71,610
Total assets	4,418,211	3,917,275	4,418,211	3,917,275
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Warehouse Lending Division
Segment Reporting Information [Line Items]
Interest income	8,476	8,988	15,289	19,315
Interest expense	1,776	268	2,142	689
Net interest income	6,700	8,720	13,147	18,626
Provision for credit losses	867	(155)	645	(300)
Noninterest income	1,041	1,333	2,442	2,313
Noninterest expense
Salaries and employee benefits	208	278	491	608
Occupancy and equipment	1	1	2	2
Data processing and communications expenses	48	68	95	117
Other expenses	212	30	430	63
Total noninterest expense	469	377	1,018	790
Income before income tax expense	6,405	9,831	13,926	20,449
Income tax expense	1,346	2,064	2,925	4,294
Net income	5,059	7,767	11,001	16,155
Total assets	923,829	779,234	923,829	779,234
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
SBA Division
Segment Reporting Information [Line Items]
Interest income	4,757	14,050	11,537	32,084
Interest expense	959	1,168	1,728	2,567
Net interest income	3,798	12,882	9,809	29,517
Provision for credit losses	(523)	(607)	(666)	(1,154)
Noninterest income	1,526	2,677	4,017	5,288
Noninterest expense
Salaries and employee benefits	1,316	937	2,587	2,319
Occupancy and equipment	81	132	180	238
Data processing and communications expenses	29	0	57	1
Other expenses	539	284	919	579
Total noninterest expense	1,965	1,353	3,743	3,137
Income before income tax expense	3,882	14,813	10,749	32,822
Income tax expense	815	3,111	2,257	6,893
Net income	3,067	11,702	8,492	25,929
Total assets	264,227	748,234	264,227	748,234
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Premium  Finance  Division
Segment Reporting Information [Line Items]
Interest income	9,436	7,368	17,095	14,379
Interest expense	1,471	321	2,084	696
Net interest income	7,965	7,047	15,011	13,683
Provision for credit losses	(94)	(794)	(311)	(236)
Noninterest income	10	4	16	8
Noninterest expense
Salaries and employee benefits	2,069	1,678	3,987	3,390
Occupancy and equipment	90	76	172	154
Data processing and communications expenses	92	94	187	181
Other expenses	1,064	852	2,016	1,773
Total noninterest expense	3,315	2,700	6,362	5,498
Income before income tax expense	4,754	5,145	8,976	8,429
Income tax expense	959	1,083	1,833	1,769
Net income	3,795	4,062	7,143	6,660
Total assets	1,071,348	880,560	1,071,348	880,560
Goodwill	64,498	64,498	64,498	64,498
Other intangible assets, net	$ 10,415	$ 13,365	$ 10,415	$ 13,365