PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 876,828	$ 117,194	$ 295,368	$ 94,747
Other assets	83,072	38,399
Total assets	6,434,296	4,921,520
Liabilities and stockholders' equity:
Subordinated debentures, net	79,059	78,920
Total liabilities	5,916,465	4,424,366
Total stockholders' equity	517,831	497,154	453,830	429,200
Total liabilities and stockholders' equity	6,434,296	4,921,520
Parent Company
Assets:
Cash and cash equivalents	280	3,663	$ 1,537	$ 7,858
Other assets	554	174
Investment in the Bank	596,703	573,410
Total assets	597,537	577,247
Liabilities and stockholders' equity:
Subordinated debentures, net	79,059	78,920
Other liabilities	647	1,173
Total liabilities	79,706	80,093
Total stockholders' equity	517,831	497,154
Total liabilities and stockholders' equity	$ 597,537	$ 577,247