SEGMENT REPORTING - Schedule of Segment Reporting, by Reportable Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Interest income	$ 76,322	$ 62,210	$ 214,783	$ 176,109
Interest expense	9,467	5,143	24,181	14,017
Net interest income	66,855	57,067	190,602	162,092
Provision for loan losses	1,787	811	5,828	2,381	$ 4,091
Noninterest income	26,999	28,864	80,894	81,529
Noninterest expense
Salaries and employee benefits	32,583	27,982	89,509	81,700
Equipment and occupancy expenses	6,036	5,989	18,059	18,060
Data processing and telecommunications expenses	7,050	6,185	20,650	18,347
Other expenses	18,098	13,043	44,381	43,051
Total noninterest expense	63,767	53,199	172,599	161,158
Income before income tax expense	28,300	31,921	93,069	80,082
Income tax expense	8,142	10,364	28,671	26,159
Net income	20,158	21,557	64,398	53,923
Total assets	7,649,820	6,493,495	7,649,820	6,493,495	6,892,031
Goodwill	125,532	122,545	125,532	122,545	125,532
Other intangible assets, net	14,437	18,472	14,437	18,472	$ 17,428
Banking Division
Segment Reporting Information [Line Items]
Interest income	59,130	55,369	170,036	158,682
Interest expense	5,530	3,716	14,510	10,726
Net interest income	53,600	51,653	155,526	147,956
Provision for loan losses	1,037	57	4,510	1,471
Noninterest income	13,007	13,949	38,974	39,702
Noninterest expense
Salaries and employee benefits	20,554	18,323	58,757	55,740
Equipment and occupancy expenses	5,384	5,490	16,068	16,541
Data processing and telecommunications expenses	6,357	5,794	18,778	17,299
Other expenses	14,905	11,533	34,355	39,040
Total noninterest expense	47,200	41,140	127,958	128,620
Income before income tax expense	18,370	24,405	62,032	57,567
Income tax expense	4,850	7,733	17,801	18,278
Net income	13,520	16,672	44,231	39,289
Total assets	6,296,159	5,841,207	6,296,159	5,841,207
Goodwill	125,532	122,545	125,532	122,545
Other intangible assets, net	14,437	18,472	14,437	18,472
Retail Mortgage Division
Segment Reporting Information [Line Items]
Interest income	5,862	3,679	14,890	9,992
Interest expense	1,597	1,054	4,179	2,383
Net interest income	4,265	2,625	10,711	7,609
Provision for loan losses	262	447	617	540
Noninterest income	12,257	13,198	35,823	36,126
Noninterest expense
Salaries and employee benefits	9,792	8,940	24,771	23,591
Equipment and occupancy expenses	555	433	1,684	1,326
Data processing and telecommunications expenses	425	364	1,182	974
Other expenses	1,001	1,303	3,030	3,392
Total noninterest expense	11,773	11,040	30,667	29,283
Income before income tax expense	4,487	4,336	15,250	13,912
Income tax expense	1,475	1,518	5,337	4,870
Net income	3,012	2,818	9,913	9,042
Total assets	531,897	356,755	531,897	356,755
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Warehouse Lending Division
Segment Reporting Information [Line Items]
Interest income	2,022	2,073	4,968	4,714
Interest expense	487	225	1,074	458
Net interest income	1,535	1,848	3,894	4,256
Provision for loan losses	215	94	159	94
Noninterest income	583	555	1,340	1,328
Noninterest expense
Salaries and employee benefits	129	103	403	399
Equipment and occupancy expenses	1	1	3	3
Data processing and telecommunications expenses	28	26	80	71
Other expenses	51	26	137	77
Total noninterest expense	209	156	623	550
Income before income tax expense	1,694	2,153	4,452	4,940
Income tax expense	580	754	1,559	1,729
Net income	1,114	1,399	2,893	3,211
Total assets	236,024	203,334	236,024	203,334
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
SBA Division
Segment Reporting Information [Line Items]
Interest income	1,413	1,089	3,884	2,721
Interest expense	432	148	1,111	450
Net interest income	981	941	2,773	2,271
Provision for loan losses	(1)	213	98	276
Noninterest income	1,130	1,162	4,663	4,373
Noninterest expense
Salaries and employee benefits	858	616	2,339	1,970
Equipment and occupancy expenses	54	65	159	190
Data processing and telecommunications expenses	9	1	12	3
Other expenses	63	181	533	542
Total noninterest expense	984	863	3,043	2,705
Income before income tax expense	1,128	1,027	4,295	3,663
Income tax expense	394	359	1,503	1,282
Net income	734	668	2,792	2,381
Total assets	94,531	92,199	94,531	92,199
Goodwill	0	0	0	0
Other intangible assets, net	0	0	0	0
Premium Finance Division
Segment Reporting Information [Line Items]
Interest income	7,895	0	21,005	0
Interest expense	1,421	0	3,307	0
Net interest income	6,474	0	17,698	0
Provision for loan losses	274	0	444	0
Noninterest income	22	0	94	0
Noninterest expense
Salaries and employee benefits	1,250	0	3,239	0
Equipment and occupancy expenses	42	0	145	0
Data processing and telecommunications expenses	231	0	598	0
Other expenses	2,078	0	6,326	0
Total noninterest expense	3,601	0	10,308	0
Income before income tax expense	2,621	0	7,040	0
Income tax expense	843	0	2,471	0
Net income	1,778	0	4,569	0
Total assets	491,209	0	491,209	0
Goodwill	0	0	0	0
Other intangible assets, net	$ 0	$ 0	$ 0	$ 0