SEGMENT REPORTING - Schedule of Segment Reporting, by Reportable Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Interest income	$ 355,146	$ 330,553	$ 1,031,921	$ 948,221
Interest expense	141,086	122,802	404,552	319,278
Net interest income	214,060	207,751	627,369	628,943
Provision for credit losses	6,107	24,459	45,985	119,704
Noninterest income	69,709	63,181	224,298	186,580
Noninterest expense
Salaries and employee benefits	88,700	81,898	259,831	244,144
Occupancy and equipment	11,716	12,745	37,160	38,253
Data processing and communications expenses	15,221	12,973	45,068	39,458
Other expenses	36,140	33,830	113,786	107,415
Total noninterest expense	151,777	141,446	455,845	429,270
Income before income tax expense	125,885	105,027	349,837	266,549
Income tax expense	26,673	24,912	85,528	63,378
Net income	99,212	80,115	264,309	203,171
Total assets	26,399,782	25,697,830	26,399,782	25,697,830	$ 25,203,699
Goodwill	1,015,646	1,015,646	1,015,646	1,015,646	1,015,646
Other intangible assets, net	74,941	92,375	74,941	92,375	$ 87,949
Banking Division
Segment Reporting Information [Line Items]
Interest income	255,241	233,214	734,220	676,003
Interest expense	78,447	63,657	219,421	155,389
Net interest income	176,794	169,557	514,799	520,614
Provision for credit losses	5,566	22,510	45,581	110,801
Noninterest income	27,800	26,824	91,690	77,455
Noninterest expense
Salaries and employee benefits	62,634	57,435	181,473	171,698
Occupancy and equipment	10,725	11,473	33,952	34,331
Data processing and communications expenses	13,922	11,818	40,862	35,596
Other expenses	22,619	20,431	71,680	67,852
Total noninterest expense	109,900	101,157	327,967	309,477
Income before income tax expense	89,128	72,714	232,941	177,791
Income tax expense	18,992	18,163	61,110	44,850
Net income	70,136	54,551	171,831	132,941
Total assets	19,387,331	18,634,055	19,387,331	18,634,055
Goodwill	951,148	951,148	951,148	951,148
Other intangible assets, net	71,164	85,648	71,164	85,648
Retail Mortgage Division
Segment Reporting Information [Line Items]
Interest income	60,789	54,532	174,889	155,988
Interest expense	37,236	31,727	104,307	91,739
Net interest income	23,553	22,805	70,582	64,249
Provision for credit losses	254	2,399	(296)	8,530
Noninterest income	41,498	35,691	130,408	106,557
Noninterest expense
Salaries and employee benefits	23,233	21,231	69,560	63,321
Occupancy and equipment	957	1,182	3,014	3,689
Data processing and communications expenses	1,184	1,052	3,826	3,518
Other expenses	12,164	12,153	38,091	35,759
Total noninterest expense	37,538	35,618	114,491	106,287
Income before income tax expense	27,259	20,479	86,795	55,989
Income tax expense	5,724	4,301	18,227	11,758
Net income	21,535	16,178	68,568	44,231
Total assets	4,899,282	4,980,246	4,899,282	4,980,246
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Warehouse Lending Division
Segment Reporting Information [Line Items]
Interest income	10,400	19,357	46,263	54,931
Interest expense	6,747	13,349	30,290	37,057
Net interest income	3,653	6,008	15,973	17,874
Provision for credit losses	(170)	(589)	334	(372)
Noninterest income	400	662	2,168	2,546
Noninterest expense
Salaries and employee benefits	621	924	2,633	2,498
Occupancy and equipment	6	1	20	2
Data processing and communications expenses	32	30	116	120
Other expenses	217	219	752	644
Total noninterest expense	876	1,174	3,521	3,264
Income before income tax expense	3,347	6,085	14,286	17,528
Income tax expense	703	1,278	3,000	3,681
Net income	2,644	4,807	11,286	13,847
Total assets	597,670	859,517	597,670	859,517
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Premium  Finance  Division
Segment Reporting Information [Line Items]
Interest income	28,716	23,450	76,549	61,299
Interest expense	18,656	14,069	50,534	35,093
Net interest income	10,060	9,381	26,015	26,206
Provision for credit losses	457	139	366	745
Noninterest income	11	4	32	22
Noninterest expense
Salaries and employee benefits	2,212	2,308	6,165	6,627
Occupancy and equipment	28	89	174	231
Data processing and communications expenses	83	73	264	224
Other expenses	1,140	1,027	3,263	3,160
Total noninterest expense	3,463	3,497	9,866	10,242
Income before income tax expense	6,151	5,749	15,815	15,241
Income tax expense	1,254	1,170	3,191	3,089
Net income	4,897	4,579	12,624	12,152
Total assets	1,515,499	1,224,012	1,515,499	1,224,012
Goodwill	64,498	64,498	64,498	64,498
Other intangible assets, net	$ 3,777	$ 6,727	$ 3,777	$ 6,727