NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net interest income	$ 46,647	$ 44,949	$ 44,329	$ 42,766	$ 39,842	$ 45,869	$ 41,104	$ 41,937	$ 178,691	$ 168,752	$ 143,388
Provision for loan losses	3,898	3,685	3,989	3,396	3,100	3,178	2,700	2,400	14,968	11,378	9,590
Net interest income after provision for loan losses									163,723	157,374	133,798
Non-interest income	14,200	14,641	14,506	4,423	15,714	12,114	15,606	14,798	47,770	58,232	54,056
Total non-interest expense	41,676	39,687	39,263	45,360	37,157	42,784	37,935	39,483	165,986	157,359	140,806
Income from continuing operations before income taxes	15,273	16,218	15,583	(1,567)	15,299	12,021	16,075	14,852	45,507	58,247	47,048
Income tax expense	3,875	4,230	4,119	(461)	4,762	3,917	4,038	4,387	11,763	17,104	13,223
Net income from continuing operations	11,398	11,988	11,464	(1,106)	10,537	8,104	12,037	10,465	33,744	41,143	33,825
(Loss) income from discontinued operations before income taxes (including gain on disposal of $63 in 2012 and $4,962 in 2011)											(261)
Gain on disposal											63
Income tax expense											376
Net loss from discontinued operations											(637)
Net income	$ 11,398	$ 11,988	$ 11,464	$ (1,106)	$ 10,537	$ 8,104	$ 12,037	$ 10,465	$ 33,744	$ 41,143	$ 33,188