SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($) banking_office segment shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) segment
Accounting Policies [Abstract]
Number of banking offices | banking_office	37
Number of reportable segments | segment	1		3
Change in Accounting Estimate [Line Items]
Salaries and employee benefits	$ 32,443,000	$ 33,469,000
Net deferred tax asset	18,673,000		$ 9,989,000
Valuation allowance	$ 0		$ 0
Shares excluded from computation of earnings per share (in shares) | shares	2,500,000
Reversal of Excess Accrual
Change in Accounting Estimate [Line Items]
Salaries and employee benefits	$ 7,800,000