PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Cash and cash equivalents	$ 295,368	$ 94,747	$ 113,838	$ 104,558
Other assets	39,188	34,329
Total assets	4,700,744	4,430,002
Liabilities and stockholders' equity:
Subordinated Debentures	78,781	78,641
Total liabilities	4,246,914	4,000,802
Total stockholders' equity	453,830	429,200	407,987	341,128
Total liabilities and stockholders' equity	4,700,744	4,430,002
Parent Company
Assets:
Cash and cash equivalents	1,537	7,858	$ 29,049	$ 25,475
Other assets	103	210
Investment in the Bank	532,105	500,896
Total assets	533,745	508,964
Liabilities and stockholders' equity:
Subordinated Debentures	78,781	78,641
Other liabilities	1,134	1,123
Total liabilities	79,915	79,764
Total stockholders' equity	453,830	429,200
Total liabilities and stockholders' equity	$ 533,745	$ 508,964