CONDENSED FINANCIAL STATEMENTS OF PARENT COMPANY - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 6,609	$ 8,617	$ 6,556	$ 4,211	$ 2,584	$ 3,632	$ 4,311	$ 4,406	$ 25,993	$ 14,933	$ 15,153
Adjustments to reconcile net income to net cash (used) provided by operating activities:
Net cash provided by operating activities									40,132	16,791	20,331
Cash flows from investing activities:
Acquisitions, net of cash paid									39,537	0	0
Net cash used in investing activities									(159,006)	(181,886)	(127,983)
Cash flows from financing activities:
Net cash provided by financing activities									201,120	163,814	107,572
Net change in cash and cash equivalents									82,246	(1,281)	(80)
Cash and cash equivalents at beginning of year				8,439				9,720	8,439	9,720	9,800
Cash and cash equivalents at end of year	90,685				8,439				90,685	8,439	9,720
Parent Company
Cash flows from operating activities:
Net income									25,993	14,933	15,153
Adjustments to reconcile net income to net cash (used) provided by operating activities:
Equity in undistributed income of subsidiaries									(15,687)	(10,380)	(11,272)
Other, net									(312)	1,336	854
Net cash provided by operating activities									9,994	5,889	4,735
Cash flows from investing activities:
Acquisitions, net of cash paid									1,939	0	0
Purchase of securities									0	0	0
Other, net									0	(1)	(1)
Net cash used in investing activities									1,939	(1)	(1)
Cash flows from financing activities:
Proceed from issuance of short term debt									0	0	0
Net proceeds from common stock									0	0	0
Net proceeds from reissuance of treasury stock									686	1,073	1,103
Common stock cash dividends paid									(11,505)	(6,577)	(6,040)
Other, net									(16)	0	0
Net cash provided by financing activities									(10,835)	(5,504)	(4,937)
Net change in cash and cash equivalents									1,098	384	(203)
Cash and cash equivalents at beginning of year				$ 1,302				$ 918	1,302	918	1,121
Cash and cash equivalents at end of year	$ 2,400				$ 1,302				$ 2,400	$ 1,302	$ 918