SEGMENT REPORTING - Schedule of Segment Reporting, by Reportable Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Interest income	$ 183,374	$ 177,950
Interest expense	10,830	12,973
Net interest income	172,544	164,977
Provision for credit losses	6,231	(28,591)
Noninterest income	86,911	117,973
Noninterest expense
Salaries and employee benefits	84,281	95,985
Occupancy and equipment	12,727	11,781
Data processing and communications expenses	12,572	11,884
Other expenses	34,240	29,148
Total noninterest expense	143,820	148,798
Income (loss) before income tax expense	109,404	162,743
Income tax expense (benefit)	27,706	37,781
Net income (loss)	81,698	124,962
Total assets	23,560,292	21,427,127	$ 23,858,321
Goodwill	1,022,345	928,005	1,012,620
Other intangible assets, net	120,757	67,848	$ 125,938
Banking Division
Segment Reporting Information [Line Items]
Interest income	129,290	112,379
Interest expense	(4,455)	(437)
Net interest income	133,745	112,816
Provision for credit losses	5,226	(23,904)
Noninterest income	21,364	16,738
Noninterest expense
Salaries and employee benefits	49,195	42,723
Occupancy and equipment	11,074	10,120
Data processing and communications expenses	11,230	10,201
Other expenses	20,045	19,710
Total noninterest expense	91,544	82,754
Income (loss) before income tax expense	58,339	70,704
Income tax expense (benefit)	16,996	18,456
Net income (loss)	41,343	52,248
Total assets	17,409,973	14,591,933
Goodwill	957,847	863,507
Other intangible assets, net	109,604	53,745
Retail Mortgage Division
Segment Reporting Information [Line Items]
Interest income	32,832	30,199
Interest expense	13,537	11,215
Net interest income	19,295	18,984
Provision for credit losses	1,587	(4,553)
Noninterest income	61,649	97,640
Noninterest expense
Salaries and employee benefits	31,614	49,838
Occupancy and equipment	1,471	1,476
Data processing and communications expenses	1,172	1,546
Other expenses	12,645	8,189
Total noninterest expense	46,902	61,049
Income (loss) before income tax expense	32,455	60,128
Income tax expense (benefit)	6,815	12,627
Net income (loss)	25,640	47,501
Total assets	4,197,613	4,086,210
Goodwill	0	0
Other intangible assets, net	0	0
Warehouse Lending Division
Segment Reporting Information [Line Items]
Interest income	6,813	10,327
Interest expense	366	421
Net interest income	6,447	9,906
Provision for credit losses	(222)	(145)
Noninterest income	1,401	980
Noninterest expense
Salaries and employee benefits	283	330
Occupancy and equipment	1	1
Data processing and communications expenses	47	49
Other expenses	218	33
Total noninterest expense	549	413
Income (loss) before income tax expense	7,521	10,618
Income tax expense (benefit)	1,579	2,230
Net income (loss)	5,942	8,388
Total assets	703,558	886,004
Goodwill	0	0
Other intangible assets, net	0	0
SBA Division
Segment Reporting Information [Line Items]
Interest income	6,780	18,034
Interest expense	769	1,399
Net interest income	6,011	16,635
Provision for credit losses	(143)	(547)
Noninterest income	2,491	2,611
Noninterest expense
Salaries and employee benefits	1,271	1,382
Occupancy and equipment	99	106
Data processing and communications expenses	28	1
Other expenses	380	295
Total noninterest expense	1,778	1,784
Income (loss) before income tax expense	6,867	18,009
Income tax expense (benefit)	1,442	3,782
Net income (loss)	5,425	14,227
Total assets	313,219	1,055,068
Goodwill	0	0
Other intangible assets, net	0	0
Premium  Finance  Division
Segment Reporting Information [Line Items]
Interest income	7,659	7,011
Interest expense	613	375
Net interest income	7,046	6,636
Provision for credit losses	(217)	558
Noninterest income	6	4
Noninterest expense
Salaries and employee benefits	1,918	1,712
Occupancy and equipment	82	78
Data processing and communications expenses	95	87
Other expenses	952	921
Total noninterest expense	3,047	2,798
Income (loss) before income tax expense	4,222	3,284
Income tax expense (benefit)	874	686
Net income (loss)	3,348	2,598
Total assets	935,929	807,912
Goodwill	64,498	64,498
Other intangible assets, net	$ 11,153	$ 14,103