PARENT COMPANY FINANCIALS ONLY (Details 2) - USD ($)		3 Months Ended									12 Months Ended
		Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Dividends received from subsidiaries(1)											$ (44,500,000)		$ (38,100,000)
Net income		$ 17,179,000		$ 20,484,000	$ 20,374,000	$ 18,611,000	$ 19,455,000	$ 18,594,000	$ 17,451,000	$ 9,460,000	76,648,000		64,960,000	$ 59,845,000
Adjustments to reconcile net income to net cash provided by operating activities
Deferred income tax expense											(5,000)		10,220,000	2,840,000
Change in other assets											7,627,000		3,842,000	(1,907,000)
Change in other liabilities											(8,738,000)		(2,450,000)	7,017,000
Net cash provided by operating activities											93,336,000		89,543,000	90,305,000
Cash flows used in investing activities
Net cash used in investing activities											(238,886,000)		(205,541,000)	(292,672,000)
Cash flows provided by financing activities
Net repayments of short-term Federal Home Loan Bank borrowings											(37,000,000)		(10,000,000)	(65,000,000)
Restricted stock awards issued, net of awards surrendered											(696,000)		(657,000)	(641,000)
Proceeds from stock issued and stock options exercised											201,000		1,367,000	2,333,000
Proceeds from shares issued under the direct stock purchase plan											2,323,000		2,695,000	1,555,000
Common dividends paid											(29,711,000)		(26,172,000)	(22,443,000)
Net cash provided by financing activities											158,880,000		213,509,000	164,296,000
Net increase (decrease) in cash and cash equivalents											13,330,000		97,511,000	(38,071,000)
Cash and cash equivalents at beginning of year						275,765,000				178,254,000	275,765,000		178,254,000	216,325,000
Cash and cash equivalents at end of period		289,095,000					275,765,000				289,095,000		275,765,000	178,254,000
Consolidation, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends received from subsidiaries(1)											(62,000)		(55,000)	(53,000)
Investments in subsidiaries		933,600,000					849,500,000				933,600,000		849,500,000
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends received from subsidiaries(1)	[1]										44,598,000		38,153,000	40,170,000
Investments in subsidiaries	[2]	935,778,000					851,743,000				935,778,000		851,743,000
Net income											76,648,000		64,960,000	59,845,000
Adjustments to reconcile net income to net cash provided by operating activities
Accretion											(154,000)		(150,000)	(194,000)
Deferred income tax expense											678,000		3,266,000	293,000
Change in other assets											423,000		7,488,000
Change in other liabilities											(5,532,000)		(254,000)	(267,000)
Equity in undistributed income of subsidiaries											(36,062,000)		(30,226,000)	(22,545,000)
Net cash provided by operating activities											36,001,000		45,084,000	37,132,000
Cash flows used in investing activities
Cash paid for acquisitions, net of cash acquired (1)											(950,000)		(51,680,000)
Net cash used in investing activities											(950,000)		(51,680,000)
Cash flows provided by financing activities
Repayment of short-term borrowings														(5,000,000)
Net repayments of short-term Federal Home Loan Bank borrowings														35,000,000
Restricted stock awards issued, net of awards surrendered											(696,000)		(657,000)	(641,000)
Proceeds from stock issued and stock options exercised											201,000		1,367,000	2,333,000
Proceeds from shares issued under the direct stock purchase plan											2,323,000		2,695,000	1,555,000
Common dividends paid											(29,711,000)		(26,172,000)	(22,443,000)
Net cash provided by financing activities											(27,883,000)		(22,767,000)	10,804,000
Net increase (decrease) in cash and cash equivalents											7,168,000		(29,363,000)	47,936,000
Cash and cash equivalents at beginning of year						$ 35,428,000				$ 64,791,000	35,428,000		64,791,000	16,855,000
Cash and cash equivalents at end of period		42,596,000					35,428,000				42,596,000		35,428,000	$ 64,791,000
Cash		$ 42,596,000	[3]				$ 35,428,000				$ 42,596,000	[3]	$ 35,428,000

[1] Income of $62,000, $55,000 and $53,000 was not eliminated in consolidation for the years ended December 31, 2016, 2015, and 2014, respectively.

[2] $933.6 million and $849.5 million eliminate in consolidation at December 31, 2016 and 2015, respectively.

[3] Entire balance eliminates in consolidation.