SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2009	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
Quarterly Financial Information Disclosure [Abstract]
Interest income		$ 51,414	$ 48,555	$ 48,426	$ 47,796	$ 48,382	$ 48,935	$ 49,474	$ 48,958	$ 196,192		$ 195,751		$ 202,724
Interest expense		5,935	5,717	5,798	5,943	6,528	7,261	7,398	7,485	23,393		28,672		38,763
Net interest income		45,479	42,838	42,628	41,853	41,854	41,674	42,076	41,473	172,799		167,079		163,961
Provision for loan losses		4,350	3,606	8,500	1,600	3,800	2,000	3,482	2,200	18,056		11,482		18,655
Other noninterest income		17,011	14,801	14,983	13,909	14,315	12,315	12,751	12,598
Net (loss)/gain on securities	1,300	5						723		5		723		458
Proceeds from life insurance policies			1,307							1,307
Total noninterest income		17,016	16,108	14,983	13,909	14,315	12,315	13,474	12,598	62,016		52,700		46,906
Other noninterest expenses		39,569	37,230	36,327	37,358	36,952	35,423	36,856	36,482	29,990		27,488		25,659
Prepayment fee on borrowings		7								(7)		(757)
Goodwill impairment			2,227							2,227	[1]		[1]		[1]
Merger and acquisition expenses		5,474	595	672						6,741
Total noninterest expenses		45,050	40,052	36,999	37,358	36,952	35,423	36,856	36,482	159,459		145,713		139,745
Provision for income taxes		3,127	3,687	3,238	4,621	4,248	4,607	4,092	4,201	14,673		17,148		12,227
Net income		$ 9,968	$ 11,601	$ 8,874	$ 12,183	$ 11,169	$ 11,959	$ 11,120	$ 11,188	$ 42,627		$ 45,436		$ 40,240
Basic earnings per share (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
Diluted earnings per share (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
Weighted average common shares (basic) (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
Common share equivalents (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

[1] Amount represents the total amount of goodwill relating to Compass Exchange Advisors, LLC, which was acquired in January 2007.