EARNINGS PER SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Net income	$ 9,968	$ 11,601	$ 8,874	$ 12,183	$ 11,169	$ 11,959	$ 11,120	$ 11,188	$ 42,627	$ 45,436	$ 40,240
Weighted Average Shares (in shares)
Basic Shares (in shares)	22,286,841	21,654,188	21,623,827	21,561,006	21,484,695	21,463,714	21,441,864	21,298,257	21,782,499	21,422,757	21,178,117
Effect of dilutive securities (in shares)	31,502	52,116	20,377	24,481	19,358	13,077	39,159	46,082	29,817	28,830	25,798
Weighted average common shares (diluted) (in shares)	22,318,343	21,706,304	21,644,204	21,585,487	21,504,053	21,476,791	21,481,023	21,344,339	21,812,316	21,451,587	21,203,915
Net Income Available to Common Shareholders per Share (in dollars per share)
Basic EPS (in dollars per share)	$ 0.45	$ 0.54	$ 0.41	$ 0.57	$ 0.52	$ 0.56	$ 0.52	$ 0.53	$ 1.96	$ 2.12	$ 1.90
Effect of Dilutive Securities (in dollars per share)									$ 0.01
Diluted EPS (in dollars per share)	$ 0.45	$ 0.53	$ 0.41	$ 0.56	$ 0.52	$ 0.56	$ 0.52	$ 0.52	$ 1.95	$ 2.12	$ 1.90