PARENT ONLY CONDENSED FINANCIAL STATEMENTS - Parent Only Condensed Statements of Operations (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
Mar. 31, 2015
Jun. 30, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Expenses                      
Interest expense                 $ 10,726 $ 8,385 $ 8,607
Salaries and benefits                 64,327 57,741 54,132
Income before income tax                 50,460 45,775 36,775
Income tax (benefit)                 12,137 10,233 7,779
Net income $ 11,744 $ 11,696 $ 6,117 $ 8,766 $ 9,108 $ 9,111 $ 7,663 $ 9,660 38,323 35,542 28,996
Comprehensive Income (Loss), Net of Tax, Attributable to Parent                 28,778 34,453 41,575
Parent Company                      
Income                      
Dividends from subsidiaries                 43,100 28,900 24,275
Fees from subsidiaries                 13,674 13,232 13,518
Other income                 13 19 526
Total income                 56,787 42,151 38,319
Expenses                      
Interest expense                 1,876 1,264 1,286
Salaries and benefits                 13,101 9,873 11,038
Professional fees                 1,364 1,238 1,372
Other expenses                 9,685 9,233 9,381
Total expenses                 26,026 21,608 23,077
Income before income tax                 30,761 20,543 15,242
Income tax (benefit)                 (4,415) (2,989) (3,118)
Income before equity in undistributed income of subsidiaries                 35,176 23,532 18,360
Equity in undistributed income (loss) of subsidiaries                 3,147 12,010 10,636
Net income                 38,323 35,542 28,996
Comprehensive Income (Loss), Net of Tax, Attributable to Parent                 $ 28,778 $ 34,453 $ 41,575