DEPOSITS (Deposit Liabilities) (Details) - USD ($)		Dec. 31, 2018	Dec. 31, 2017
Deposit Liabilities [Line Items]
Non-interest-bearing checking		$ 3,657,817,000	$ 3,265,544,000
Interest-bearing checking		1,191,016,000	971,137,000
Regular savings accounts		1,842,581,000	1,557,500,000
Money market accounts		1,465,369,000	1,422,313,000
Total interest-bearing transaction and savings accounts		4,498,966,000	3,950,950,000
Time Deposits, $250,000 or less		1,143,303,000	813,997,000
Time Deposits, More than $250,000		176,962,000	152,940,000
Interest-bearing certificates	[1]	1,320,265,000	966,937,000
Total deposits		9,477,048,000	8,183,431,000
Included in total deposits:
Public fund transaction accounts		217,401,000	198,719,000
Public fund interest-bearing certificates		30,089,000	23,685,000
Total public deposits		247,490,000	222,404,000
Total brokered deposits		377,347,000	57,228,000
Related Party Deposit Liabilities		8,300,000	10,000,000
Business Combination, Acquired Deposits, Time Deposit Premium		563,000	11,000
Time deposits equal to or greater than $250,000		$ 180,500,000	$ 155,900,000

[1] )Certificates of deposit included $563,000 of acquisition discounts at December 31, 2018 and $11,000 of acquisition premiums at December 31, 2017.