PARENT COMPANY FINANCIAL INFORMATION (Tables) - Parent Company
   | 
12 Months Ended | 
Dec. 31, 2019  | 
| Financial Information for the Parent Company - Balance Sheets | 
 Financial information for the Parent Company is as follows: 
PARENT COMPANY 
CONDENSED BALANCE SHEETS 
AS OF DECEMBER 31, 2019 and 2018 
(Dollars in thousands) 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 
  | 
      | 
2019  | 
      | 
2018  | 
 
ASSETS  | 
   | 
  | 
    | 
   | 
  | 
    | 
 
Cash  | 
  | 
$  | 
 5,283  | 
  | 
$  | 
 3,681  | 
 
Premises and equipment, net  | 
  | 
   | 
 10,568  | 
  | 
   | 
 10,637  | 
 
Other assets  | 
  | 
   | 
 27,438  | 
  | 
   | 
 13,386  | 
 
Investment in subsidiaries  | 
  | 
   | 
 2,786,842  | 
  | 
   | 
 2,202,530  | 
 
Total assets  | 
  | 
$  | 
 2,830,131  | 
  | 
$  | 
 2,230,234  | 
 
LIABILITIES AND STOCKHOLDERS' EQUITY  | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Short-term borrowings  | 
  | 
   | 
 —  | 
  | 
   | 
 5,000  | 
 
Long-term borrowings  | 
  | 
   | 
 157,155  | 
  | 
   | 
 157,057  | 
 
Trust preferred capital notes  | 
  | 
   | 
 140,237  | 
  | 
   | 
 134,342  | 
 
Other liabilities  | 
  | 
   | 
 19,637  | 
  | 
   | 
 9,254  | 
 
Total liabilities  | 
  | 
   | 
 317,029  | 
  | 
   | 
 305,653  | 
 
Total stockholders' equity  | 
  | 
   | 
 2,513,102  | 
  | 
   | 
 1,924,581  | 
 
Total liabilities and stockholders' equity  | 
  | 
$  | 
 2,830,131  | 
  | 
$  | 
 2,230,234  | 
 
 
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| Financial Information for the Parent Company - Statements of Income and Comprehensive Income | 
 PARENT COMPANY 
CONDENSED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME 
YEARS ENDED DECEMBER 31, 2019, 2018, and 2017 
(Dollars in thousands) 
 
 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
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  | 
      | 
2019  | 
      | 
2018  | 
      | 
  | 
2017  | 
 
Income:  | 
   | 
  | 
    | 
   | 
  | 
    | 
   | 
  | 
    | 
 
Interest and dividend income  | 
  | 
$  | 
 3  | 
  | 
$  | 
 —  | 
  | 
$  | 
 3  | 
 
Dividends received from subsidiaries  | 
  | 
   | 
 160,033  | 
  | 
   | 
 50,750  | 
  | 
   | 
 33,350  | 
 
Other operating income  | 
  | 
   | 
 1,484  | 
  | 
   | 
 2,719  | 
  | 
   | 
 1,308  | 
 
Total income  | 
  | 
   | 
 161,520  | 
  | 
   | 
 53,469  | 
  | 
   | 
 34,661  | 
 
Expenses:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Interest expense  | 
  | 
   | 
 15,935  | 
  | 
   | 
 15,253  | 
  | 
   | 
 11,423  | 
 
Other operating expenses  | 
  | 
   | 
 11,434  | 
  | 
   | 
 13,782  | 
  | 
   | 
 7,130  | 
 
Total expenses  | 
  | 
   | 
 27,369  | 
  | 
   | 
 29,035  | 
  | 
   | 
 18,553  | 
 
Income before income taxes and equity in undistributed net income from subsidiaries  | 
  | 
   | 
 134,151  | 
  | 
   | 
 24,434  | 
  | 
   | 
 16,108  | 
 
Income tax benefit  | 
  | 
   | 
 (6,499)  | 
  | 
   | 
 (6,176)  | 
  | 
   | 
 (9,169)  | 
 
Equity in undistributed net income from subsidiaries  | 
  | 
   | 
 52,878  | 
  | 
   | 
 115,638  | 
  | 
   | 
 47,646  | 
 
Net income  | 
  | 
$  | 
 193,528  | 
  | 
$  | 
 146,248  | 
  | 
$  | 
 72,923  | 
 
Comprehensive income  | 
  | 
$  | 
 239,376  | 
  | 
$  | 
 136,905  | 
  | 
$  | 
 75,848  | 
 
 
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| Financial Information for the Parent Company - Statements of Cash Flows | 
 PARENT COMPANY 
CONDENSED STATEMENTS OF CASH FLOWS 
YEARS ENDED DECEMBER 31, 2019, 2018, and 2017 
(Dollars in thousands) 
 
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  | 
      | 
2019  | 
      | 
2018  | 
      | 
2017  | 
 
Operating activities:  | 
   | 
  | 
    | 
   | 
  | 
    | 
   | 
  | 
    | 
 
Net income  | 
  | 
$  | 
 193,528  | 
  | 
$  | 
 146,248  | 
  | 
$  | 
 72,923  | 
 
Adjustments to reconcile net income to net cash provided by operating activities:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Equity in undistributed net income of subsidiaries  | 
  | 
   | 
 (52,878)  | 
  | 
   | 
 (115,638)  | 
  | 
   | 
 (47,646)  | 
 
Depreciation of premises and equipment  | 
  | 
   | 
 424  | 
  | 
   | 
 424  | 
  | 
   | 
 439  | 
 
Acquisition accounting amortization, net  | 
  | 
   | 
 662  | 
  | 
   | 
 636  | 
  | 
   | 
 260  | 
 
Gain on sale of investment  | 
  | 
   | 
 —  | 
  | 
   | 
 (1,416)  | 
  | 
   | 
 —  | 
 
Issuance of common stock for services  | 
  | 
   | 
 910  | 
  | 
   | 
 914  | 
  | 
   | 
 724  | 
 
Net (increase) decrease in other assets  | 
  | 
   | 
 (3,256)  | 
  | 
   | 
 (584)  | 
  | 
   | 
 (4,167)  | 
 
Net increase in other liabilities  | 
  | 
   | 
 4,964  | 
  | 
   | 
 (4,159)  | 
  | 
   | 
 5,283  | 
 
Net cash and cash equivalents provided by (used in) operating activities  | 
  | 
   | 
 144,354  | 
  | 
   | 
 26,425  | 
  | 
   | 
 27,816  | 
 
Investing activities:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Net increase in premises and equipment  | 
  | 
   | 
 (355)  | 
  | 
   | 
 —  | 
  | 
   | 
 (35)  | 
 
Proceeds from sale of investment  | 
  | 
   | 
 —  | 
  | 
   | 
 3,761  | 
  | 
   | 
 —  | 
 
Proceeds from (payments for) equity method investment  | 
  | 
   | 
 —  | 
  | 
   | 
 —  | 
  | 
   | 
 72  | 
 
Cash paid in acquisitions  | 
  | 
  | 
 (12)  | 
  | 
  | 
 —  | 
  | 
  | 
 —  | 
 
Cash received in acquisitions  | 
  | 
   | 
 21,553  | 
  | 
   | 
 25,976  | 
  | 
   | 
 —  | 
 
Net cash and cash equivalents provided by (used in) investing activities  | 
  | 
   | 
 21,186  | 
  | 
   | 
 29,737  | 
  | 
   | 
 37  | 
 
Financing activities:  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Net increase (decrease) in short-term borrowings  | 
  | 
   | 
 (5,000)  | 
  | 
   | 
 5,000  | 
  | 
   | 
 —  | 
 
Cash dividends paid - common stock  | 
  | 
   | 
 (78,345)  | 
  | 
   | 
 (58,001)  | 
  | 
   | 
 (35,393)  | 
 
Cancellation of warrants  | 
  | 
   | 
 —  | 
  | 
   | 
 (1,530)  | 
  | 
   | 
 —  | 
 
Issuance (repurchase) of common stock  | 
  | 
   | 
 (78,292)  | 
  | 
   | 
 2,347  | 
  | 
   | 
 1,037  | 
 
Vesting of restricted stock, net of shares held for taxes  | 
  | 
   | 
 (2,301)  | 
  | 
   | 
 (2,908)  | 
  | 
   | 
 (1,567)  | 
 
Net cash and cash equivalents provided by (used in) financing activities  | 
  | 
   | 
 (163,938)  | 
  | 
   | 
 (55,092)  | 
  | 
   | 
 (35,923)  | 
 
Increase (decrease) in cash and cash equivalents  | 
  | 
   | 
 1,602  | 
  | 
   | 
 1,070  | 
  | 
   | 
 (8,070)  | 
 
Cash and cash equivalents at beginning of the period  | 
  | 
   | 
 3,681  | 
  | 
   | 
 2,611  | 
  | 
   | 
 10,681  | 
 
Cash and cash equivalents at end of the period  | 
  | 
$  | 
 5,283  | 
  | 
$  | 
 3,681  | 
  | 
$  | 
 2,611  | 
 
Supplemental schedule of noncash investing and financing activities  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Issuance of common stock in exchange for net assets in acquisition  | 
  | 
$  | 
 499,974  | 
  | 
$  | 
 794,809  | 
  | 
$  | 
 —  | 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
 
Transactions related to bank acquisition  | 
  | 
   | 
    | 
  | 
   | 
    | 
  | 
   | 
    | 
 
Assets acquired  | 
  | 
   | 
 509,075  | 
  | 
   | 
 859,176  | 
  | 
   | 
 —  | 
 
Liabilities assumed  | 
  | 
   | 
 9,089  | 
  | 
   | 
 64,367  | 
  | 
   | 
 —  | 
 
 
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