SEGMENT REPORTING - Schedule of Financial Information with Respect to Company's Reportable Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Interest income	$ 703,112	$ 726,503	$ 636,394
Interest expense	47,785	88,750	131,228
Net interest income	655,327	637,753	505,166
Provision for credit losses	(35,365)	145,380	19,758
Noninterest income	365,544	446,500	198,113
Noninterest expense
Salaries and employee benefits	337,776	360,278	223,938
Occupancy and equipment expenses	48,066	52,349	40,596
Data processing and communications expenses	45,976	46,017	38,513
Other expenses	128,306	139,985	168,890
Total noninterest expense	560,124	598,629	471,937
Income before income tax expense	496,112	340,244	211,584
Income tax expense	119,199	78,256	50,143
Net income	376,913	261,988	161,441
Total assets	23,858,321	20,438,638	18,242,579
Goodwill	1,012,620	928,005	931,637
Other intangible assets, net	125,938	71,974	91,586
Banking Division
Segment Reporting Information [Line Items]
Interest income	449,955	499,031	478,340
Interest expense	(7,627)	27,800	59,327
Net interest income	457,582	471,231	419,013
Provision for credit losses	(32,866)	125,136	12,654
Noninterest income	69,664	63,165	69,005
Noninterest expense
Salaries and employee benefits	157,079	160,430	130,134
Occupancy and equipment expenses	41,065	44,939	35,281
Data processing and communications expenses	39,802	39,040	34,934
Other expenses	84,244	105,965	149,919
Total noninterest expense	322,190	350,374	350,268
Income before income tax expense	237,922	58,886	125,096
Income tax expense	64,446	19,138	31,609
Net income	173,476	39,748	93,487
Total assets	17,537,221	14,250,780	13,063,461
Goodwill	948,122	863,507	867,139
Other intangible assets, net	114,048	57,129	73,737
Retail Mortgage Division
Segment Reporting Information [Line Items]
Interest income	130,140	129,951	88,129
Interest expense	47,422	47,592	43,577
Net interest income	82,718	82,359	44,552
Provision for credit losses	2,947	15,850	3,472
Noninterest income	281,900	370,256	118,188
Noninterest expense
Salaries and employee benefits	167,796	184,765	82,470
Occupancy and equipment expenses	6,206	6,710	4,666
Data processing and communications expenses	5,551	6,275	2,418
Other expenses	38,295	28,155	12,536
Total noninterest expense	217,848	225,905	102,090
Income before income tax expense	143,823	210,860	57,178
Income tax expense	30,203	44,286	12,202
Net income	113,620	166,574	44,976
Total assets	4,231,767	3,395,811	3,636,321
Goodwill	0	0	0
Other intangible assets, net	0	0	0
Warehouse Lending Division
Segment Reporting Information [Line Items]
Interest income	36,784	26,522	22,370
Interest expense	1,383	2,631	9,753
Net interest income	35,401	23,891	12,617
Provision for credit losses	(514)	2,562	67
Noninterest income	4,603	3,864	1,999
Noninterest expense
Salaries and employee benefits	1,130	981	934
Occupancy and equipment expenses	3	4	5
Data processing and communications expenses	232	270	156
Other expenses	490	176	223
Total noninterest expense	1,855	1,431	1,318
Income before income tax expense	38,663	23,762	13,231
Income tax expense	8,120	5,004	2,778
Net income	30,543	18,758	10,453
Total assets	760,546	922,071	527,527
Goodwill	0	0	0
Other intangible assets, net	0	0	0
SBA Division
Segment Reporting Information [Line Items]
Interest income	56,597	40,334	12,735
Interest expense	5,062	7,244	5,704
Net interest income	51,535	33,090	7,031
Provision for credit losses	(2,921)	2,719	544
Noninterest income	9,360	9,200	8,915
Noninterest expense
Salaries and employee benefits	4,856	6,893	4,783
Occupancy and equipment expenses	475	391	269
Data processing and communications expenses	47	33	32
Other expenses	1,594	1,832	1,651
Total noninterest expense	6,972	9,149	6,735
Income before income tax expense	56,844	30,422	8,667
Income tax expense	11,937	6,389	1,820
Net income	44,907	24,033	6,847
Total assets	419,040	1,088,611	267,273
Goodwill	0	0	0
Other intangible assets, net	0	0	0
Premium Finance Division
Segment Reporting Information [Line Items]
Interest income	29,636	30,665	34,820
Interest expense	1,545	3,483	12,867
Net interest income	28,091	27,182	21,953
Provision for credit losses	(2,011)	(887)	3,021
Noninterest income	17	15	6
Noninterest expense
Salaries and employee benefits	6,915	7,209	5,617
Occupancy and equipment expenses	317	305	375
Data processing and communications expenses	344	399	973
Other expenses	3,683	3,857	4,561
Total noninterest expense	11,259	11,770	11,526
Income before income tax expense	18,860	16,314	7,412
Income tax expense	4,493	3,439	1,734
Net income	14,367	12,875	5,678
Total assets	909,747	781,365	747,997
Goodwill	64,498	64,498	64,498
Other intangible assets, net	$ 11,890	$ 14,845	$ 17,849