PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net income	$ 51,691	$ 39,227	$ 20,539
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
(Increase) decrease in other assets	3,942	(2,373)	5,426
Increase (decrease) in other liabilities	(1,509)	3,430	4,194
Net cash provided by operating activities	69,962	58,383	46,826
Cash flows from investing activities:
Net cash used in investing activities	(352,606)	(80,549)	(411,784)
Cash flows from financing activities:
Net proceeds from issuance of common stock	1,102	1,017	951
Purchase of treasury stock	(625)
Repurchase of surrendered stock from vesting of stock plans	(887)	(586)	(350)
Cash dividends paid	(18,420)	(18,342)	(18,238)
Net cash used in financing activities	104,470	222,787	345,867
Net (decrease) increase in cash and cash equivalents	(178,174)	200,621	(19,091)
Cash and cash equivalents at beginning of period	295,368	94,747	113,838
Cash and cash equivalents at end of period	117,194	295,368	94,747
Parent Company
Cash flows from operating activities:
Net income	51,691	39,227	20,539
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed earnings of the Bank	(30,840)	(27,896)	(23,500)
Amortization	139	140	139
(Increase) decrease in other assets	(73)	108	18
Increase (decrease) in other liabilities	39	11	(398)
Net cash provided by operating activities	20,956	11,590	(3,202)
Cash flows from financing activities:
Repayment of junior subordinated debentures	0	0	(352)
Net proceeds from issuance of common stock	1,102	1,017	951
Purchase of treasury stock	(625)
Repurchase of surrendered stock from vesting of stock plans	(887)	(586)	(350)
Cash dividends paid	(18,420)	(18,342)	(18,238)
Net cash used in financing activities	(18,830)	(17,911)	(17,989)
Net (decrease) increase in cash and cash equivalents	2,126	(6,321)	(21,191)
Cash and cash equivalents at beginning of period	1,537	7,858	29,049
Cash and cash equivalents at end of period	$ 3,663	$ 1,537	$ 7,858