PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 42,042	$ 51,691	$ 39,227
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in other assets	(11,916)	3,942	(2,373)
(Decrease) increase in other liabilities	(5,371)	(1,509)	3,430
Net cash provided by operating activities	47,387	69,962	58,383
Cash flows from investing activities:
Net cash used in investing activities	(716,840)	(352,606)	(80,549)
Cash flows from financing activities:
Net proceeds from issuance of common stock	1,267	1,102	1,017
Purchase of treasury stock	(4,633)	(625)
Repurchase of surrendered stock from vesting of stock plans	(3,181)	(887)	(586)
Cash dividends paid	(19,197)	(18,420)	(18,342)
Net cash provided by financing activities	1,429,087	104,470	222,787
Net increase (decrease) in cash and cash equivalents	759,634	(178,174)	200,621
Cash and cash equivalents at beginning of period	117,194	295,368	94,747
Cash and cash equivalents at end of period	876,828	117,194	295,368
Parent Company
Cash flows from operating activities:
Net income	42,042	51,691	39,227
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of the Bank	(18,915)	(30,840)	(27,896)
Amortization	139	139	140
(Increase) decrease in other assets	(379)	(73)	108
(Decrease) increase in other liabilities	(526)	39	11
Net cash provided by operating activities	22,361	20,956	11,590
Cash flows from financing activities:
Net proceeds from issuance of common stock	1,267	1,102	1,017
Purchase of treasury stock	(4,633)	(625)
Repurchase of surrendered stock from vesting of stock plans	(3,181)	(887)	(586)
Cash dividends paid	(19,197)	(18,420)	(18,342)
Net cash provided by financing activities	(25,744)	(18,830)	(17,911)
Net increase (decrease) in cash and cash equivalents	(3,383)	2,126	(6,321)
Cash and cash equivalents at beginning of period	3,663	1,537	7,858
Cash and cash equivalents at end of period	$ 280	$ 3,663	$ 1,537