ACQUISITION OF CORNERSTONE BANCORP, INC. - CONTRIBUTION (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
INTEREST INCOME:                      
Loans, including fees                 $ 164,232 $ 133,958 $ 123,360
Taxable investment securities                 7,876 7,046 7,481
Total interest income $ 45,903 $ 43,934 $ 40,140 $ 44,015 $ 36,842 $ 36,107 $ 35,722 $ 33,761 173,992 142,432 132,377
INTEREST EXPENSE:                      
Subordinated note                 915 2,056 2,515
NET INTEREST INCOME 41,645 39,398 35,577 39,434 32,466 31,424 31,058 29,022 156,054 123,970 112,773
Provision for loan and lease losses 5,004 2,489 1,814 5,186 2,074 2,233 904 185 14,493 5,396 2,859
NET INTEREST INCOME AFTER PROVISION FOR LOAN AND LEASE LOSSES 36,641 36,909 33,763 34,248 30,392 29,191 30,154 28,837 141,561 118,574 109,914
NONINTEREST INCOME:                      
Service charges on deposit accounts                 13,176 13,015 13,807
Interchange fee income                 9,009 8,353 7,017
Other                 4,398 2,405 3,001
Total noninterest income 10,485 11,301 10,802 24,921 7,717 7,806 9,485 22,986 57,509 47,994 42,519
NONINTEREST EXPENSES:                      
Salaries and employee benefits                 69,882 58,091 54,373
Occupancy and equipment, net                 21,777 20,689 22,008
Communication and transportation                 4,256 3,752 3,866
Marketing and development                 3,778 3,161 3,264
FDIC insurance expense                 1,780 2,084 1,865
Data processing                 6,121 4,340 3,513
Supplies                 1,406 1,101 1,009
Legal and professional fees                 2,556 3,306 2,766
Other                 8,305 7,458 6,364
Total noninterest expenses 32,166 33,534 31,866 32,541 26,847 28,238 27,165 31,074 130,107 113,324 108,118
INCOME BEFORE INCOME TAX EXPENSE 14,960 14,676 12,699 26,628 11,262 8,759 12,474 20,749 68,963 53,244 44,315
Income tax expense (benefit) 4,960 4,848 4,359 8,893 3,844 3,119 4,154 6,961 23,060 18,078 15,528
NET INCOME $ 10,000 $ 9,828 $ 8,340 $ 17,735 $ 7,418 $ 5,640 $ 8,320 $ 13,788 45,903 $ 35,166 $ 28,787
Cornerstone                      
INTEREST INCOME:                      
Loans, including fees                 5,903    
Taxable investment securities                 1,331    
Total interest income                 7,234    
INTEREST EXPENSE:                      
Deposits                 348    
Borrowings                 1,931    
Subordinated note                 37    
Total interest expense                 2,316    
NET INTEREST INCOME                 4,918    
Provision for loan and lease losses                 327    
NET INTEREST INCOME AFTER PROVISION FOR LOAN AND LEASE LOSSES                 4,591    
NONINTEREST INCOME:                      
Service charges on deposit accounts                 210    
Interchange fee income                 133    
Other                 192    
Total noninterest income                 535    
NONINTEREST EXPENSES:                      
Salaries and employee benefits                 2,096    
Occupancy and equipment, net                 532    
Communication and transportation                 196    
Marketing and development                 144    
FDIC insurance expense                 44    
Data processing                 628    
Supplies                 69    
Legal and professional fees                 211    
Other                 499    
Total noninterest expenses                 4,419    
INCOME BEFORE INCOME TAX EXPENSE                 707    
Income tax expense (benefit)                 216    
NET INCOME                 491    
Cornerstone | Non-Acquisition Related                      
INTEREST INCOME:                      
Loans, including fees                 5,663    
Taxable investment securities                 1,331    
Total interest income                 6,994    
INTEREST EXPENSE:                      
Deposits                 362    
Borrowings                 1,931    
Subordinated note                 37    
Total interest expense                 2,330    
NET INTEREST INCOME                 4,664    
Provision for loan and lease losses                 327    
NET INTEREST INCOME AFTER PROVISION FOR LOAN AND LEASE LOSSES                 4,337    
NONINTEREST INCOME:                      
Service charges on deposit accounts                 210    
Interchange fee income                 133    
Other                 192    
Total noninterest income                 535    
NONINTEREST EXPENSES:                      
Salaries and employee benefits                 1,822    
Occupancy and equipment, net                 532    
Communication and transportation                 186    
Marketing and development                 144    
FDIC insurance expense                 44    
Data processing                 11    
Supplies                 49    
Legal and professional fees                 73    
Other                 364    
Total noninterest expenses                 3,225    
INCOME BEFORE INCOME TAX EXPENSE                 1,647    
Income tax expense (benefit)                 506    
NET INCOME                 1,141    
Cornerstone | Acquisition-Related                      
INTEREST INCOME:                      
Loans, including fees                 240    
Total interest income                 240    
INTEREST EXPENSE:                      
Deposits                 (14)    
Total interest expense                 (14)    
NET INTEREST INCOME                 254    
NET INTEREST INCOME AFTER PROVISION FOR LOAN AND LEASE LOSSES                 254    
NONINTEREST EXPENSES:                      
Salaries and employee benefits                 274    
Communication and transportation                 10    
Data processing                 617    
Supplies                 20    
Legal and professional fees                 138    
Other                 135    
Total noninterest expenses                 1,194    
INCOME BEFORE INCOME TAX EXPENSE                 (940)    
Income tax expense (benefit)                 (290)    
NET INCOME                 $ (650)