PARENT COMPANY STATEMENTS (CONDENSED STATEMENTS OF CASH FLOWS) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 21,363	$ 20,570	$ 20,142	$ 18,336	$ 11,627	$ 15,825	$ 15,364	$ 14,514	$ 80,411	$ 57,330	$ 52,084
Adjustments to net cash from operating activities:
Net cash from operating activities									104,975	77,242	62,199
Cash flows from financing activities:
Purchase of treasury stock									(463)	(495)	(458)
Sales of treasury stock									115	0	0
Net cash from financing activities									102,209	327,708	466,855
Net change in cash and cash equivalents									40,742	8,900	86,606
Cash and cash equivalents at beginning of the year				176,180				167,280	176,180	167,280	80,674
Cash and cash equivalents at end of the year	216,922				176,180				216,922	176,180	167,280
Parent Company [Member]
Cash flows from operating activities:
Net income									80,411	57,330	52,084
Adjustments to net cash from operating activities:
Equity in undistributed income of subsidiaries									(56,567)	(39,573)	(34,090)
Other changes									7,294	3,586	3,818
Net cash from operating activities									31,138	21,343	21,812
Cash flows from financing activities:
Proceeds (Payments) related to equity incentive plans									(2,435)	(1,736)	614
Purchase of treasury stock									(463)	(495)	(458)
Sales of treasury stock									115	0	0
Dividends paid									(25,278)	(21,396)	(18,200)
Net cash from financing activities									(28,061)	(23,627)	(18,044)
Net change in cash and cash equivalents									3,077	(2,284)	3,768
Cash and cash equivalents at beginning of the year				$ 5,819				$ 8,103	5,819	8,103	4,335
Cash and cash equivalents at end of the year	$ 8,896				$ 5,819				$ 8,896	$ 5,819	$ 8,103