PARENT COMPANY ONLY FINANCIAL INFORMATION (Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Cash and interest bearing deposits	$ 337,903	$ 378,734
Other assets	281,024	186,755
TOTAL ASSETS	17,908,339	13,209,597
Liabilities and Stockholders’ equity:
Other borrowings	457,042	275,773
Accrued expenses and other liabilities	224,289	128,730
TOTAL LIABILITIES	15,829,108	11,631,460
Stockholders’ equity:
Common stock	42,094	36,704
Capital surplus	1,062,083	839,857
Retained earnings	791,630	702,502
Accumulated other comprehensive income (loss)	72,719	(926)
TOTAL STOCKHOLDERS' EQUITY	2,079,231	1,578,137	$ 1,325,175	$ 991,457
TOTAL LIABILITIES AND EQUITY	17,908,339	13,209,597
Parent
Assets:
Cash and interest bearing deposits	84,728	61,866
Investment in subsidiaries	2,234,813	1,765,995
Other assets	68,263	49,002
TOTAL ASSETS	2,387,804	1,876,863
Liabilities and Stockholders’ equity:
Other borrowings	265,168	271,046
Accrued expenses and other liabilities	43,405	27,680
TOTAL LIABILITIES	308,573	298,726
Stockholders’ equity:
Preferred stock	110,705	0
Common stock	42,094	36,704
Capital surplus	1,062,083	839,857
Retained earnings	791,630	702,502
Accumulated other comprehensive income (loss)	72,719	(926)
TOTAL STOCKHOLDERS' EQUITY	2,079,231	1,578,137
TOTAL LIABILITIES AND EQUITY	$ 2,387,804	$ 1,876,863