INCOME TAXES - PROVISION AND DEFERRED TAX (Details) - USD ($)
$ in Thousands
 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
Current expense:                      
Federal                 $ 24,295 $ 18,108 $ 22,143
State                 465 1,125 2,469
Deferred expense:                      
Federal                 (1,753) (1,262) (8,637)
State                 53 107 (447)
Total $ 4,960 $ 4,848 $ 4,359 $ 8,893 $ 3,844 $ 3,119 $ 4,154 $ 6,961 $ 23,060 $ 18,078 $ 15,528
Effective tax rate that differs from that computed at the federal statutory rate                      
Federal statutory rate times financial statement income                 35.00% 35.00% 35.00%
Effect of:                      
State taxes, net of federal benefit (as a percent)                 0.49% 1.50% 2.96%
General business tax credits (as a percent)                 (0.33%) (0.43%) (0.67%)
Nontaxable income                 (2.12%) (2.68%) (2.80%)
Other, net (as a percent)                 0.39% 0.56% 0.55%
Effective tax rate                 33.43% 33.95% 35.04%
Deferred tax assets:                      
Allowance for loan and leases losses 10,824       9,595       $ 10,824 $ 9,595  
Accrued expenses 5,733       3,913       5,733 3,913  
Net operating loss carryforward 5,417       1,574       5,417 1,574  
Depreciation         1,289         1,289  
Other-than-temporary impairment 746       750       746 750  
Partnership losses 879       842       879 842  
OREO Writedowns 19       20       19 20  
Fair value of cash flow hedges 138       210       138 210  
Acquisition fair value adjustments 1,379               1,379    
Other 2,237       2,061       2,237 2,061  
Total deferred tax assets 27,372       20,254       27,372 20,254  
Deferred tax liabilities:                      
Unrealized investment securities gains (711)       (1,314)       (711) (1,314)  
Federal Home Loan Bank dividends (4,296)       (4,315)       (4,296) (4,315)  
Deferred loan fees (162)       (317)       (162) (317)  
Mortgage servicing rights (1,870)       (1,781)       (1,870) (1,781)  
Bargain purchase gain (1,436)       (552)       (1,436) (552)  
New market tax credits (831)       (707)       (831) (707)  
Depreciation and amortization (138)               (138)    
Other (1,127)       (374)       (1,127) (374)  
Total deferred tax liabilities (10,571)       (9,360)       (10,571) (9,360)  
Less: Valuation allowance (1,635)       (1,564)       (1,635) (1,564)  
Net deferred tax asset $ 15,166       $ 9,330       $ 15,166 $ 9,330