PARENT COMPANY ONLY CONDENSED FINANCIAL INFORMATION - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 39,227	$ 20,539	$ 35,491
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Decrease (increase) in other assets	2,373	(5,426)	(8,331)
Increase (decrease) in other liabilities	3,430	4,194	(6,476)
Net cash provided by operating activities	58,383	46,826	44,236
Cash flows from investing activities:
Net cash used in investing activities	(80,549)	(411,784)	(279,545)
Cash flows from financing activities:
Net proceeds from issuance of common stock	1,017	951	48,442
Net proceeds from exercise of stock options			62
Repurchase of surrendered stock from vesting of restricted stock awards	(586)	(350)	(344)
Cash dividends paid	(18,342)	(18,238)	(16,140)
Net cash provided by financing activities	222,787	345,867	244,589
Net increase (decrease) in cash and cash equivalents	200,621	(19,091)	9,280
Cash and cash equivalents at beginning of period	94,747	113,838	104,558
Cash and cash equivalents at end of period	295,368	94,747	113,838
Parent Company
Cash flows from operating activities:
Net income	39,227	20,539	35,491
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed earnings of the Bank	(27,896)	(23,500)	(24,728)
Amortization	140	139	152
Decrease (increase) in other assets	108	18	(212)
Increase (decrease) in other liabilities	11	(398)	351
Net cash provided by operating activities	11,590	(3,202)	11,054
Cash flows from investing activities:
Investment in the Bank	0	0	(39,500)
Net cash used in investing activities	0	0	(39,500)
Cash flows from financing activities:
Repayment of junior subordinated debentures	0	(352)	0
Net proceeds from issuance of common stock	1,017	951	48,442
Net proceeds from exercise of stock options	0	0	62
Repurchase of surrendered stock from vesting of restricted stock awards	(586)	(350)	(344)
Cash dividends paid	(18,342)	(18,238)	(16,140)
Net cash provided by financing activities	(17,911)	(17,989)	32,020
Net increase (decrease) in cash and cash equivalents	(6,321)	(21,191)	3,574
Cash and cash equivalents at beginning of period	7,858	29,049	25,475
Cash and cash equivalents at end of period	$ 1,537	$ 7,858	$ 29,049