LOANS - Allowance for loan losses and recorded investment (Details) - 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
Changes in allowance for loan losses :
Beginning balance				$ 15,988,000				$ 12,300,000	$ 15,988,000	$ 12,300,000	$ 23,672,000
Provision for loan losses	$ 2,445,000	$ 1,392,000	$ 629,000	1,125,000	$ 1,052,000	$ 6,699,000	$ 2,379,000	997,000	5,591,000	11,127,000	92,000
Charge-offs									(7,736,000)	(9,657,000)	(12,096,000)
Recoveries									1,019,000	2,218,000	632,000
Net loan charge-offs									(6,717,000)	(7,439,000)	(11,464,000)
Ending balance	14,862,000				15,988,000				14,862,000	15,988,000	12,300,000
Non-PCI loans
Changes in allowance for loan losses :
Beginning balance				14,093,000				10,503,000	14,093,000	10,503,000	11,985,000
Provision for loan losses									6,425,000	11,061,000	300,000
Charge-offs									(7,668,000)	(9,565,000)	(2,271,000)
Recoveries									894,000	2,094,000	489,000
Net loan charge-offs									(6,774,000)	(7,471,000)	(1,782,000)
Ending balance	13,744,000				14,093,000				13,744,000	14,093,000	10,503,000
Non-PCI loans | Nonpeforming, one borrower
Changes in allowance for loan losses :
Charge-offs									(1,600,000)
Non-PCI loans | Nonpeforming, single credit relationship borrower
Changes in allowance for loan losses :
Charge-offs									(530,000)
Non-PCI loans | Nonperforming, group of nonperforming loans
Changes in allowance for loan losses :
Charge-offs										(7,500,000)
Non-PCI loans | Nonperforming financial instruments second single borrower
Changes in allowance for loan losses :
Charge-offs									(1,400,000)
PCI loans
Changes in allowance for loan losses :
Beginning balance				$ 1,895,000				$ 1,797,000	1,895,000	1,797,000	11,687,000
Provision for loan losses									(834,000)	66,000	(208,000)
Charge-offs									(68,000)	(92,000)	(9,825,000)
Recoveries									125,000	124,000	143,000
Net loan charge-offs									57,000	32,000	(9,682,000)
Ending balance	$ 1,118,000				$ 1,895,000				$ 1,118,000	$ 1,895,000	$ 1,797,000