DEPOSITS (Deposit Liabilities) (Details) - USD ($)		Dec. 31, 2021	Dec. 31, 2020
Deposit Liabilities [Line Items]
Non-interest-bearing checking		$ 6,385,177,000	$ 5,492,924,000
Interest-bearing checking		1,947,414,000	1,569,435,000
Regular savings accounts		2,784,716,000	2,398,482,000
Money market accounts		2,370,995,000	2,191,135,000
Total interest-bearing transaction and savings accounts		7,103,125,000	6,159,052,000
Time Deposits, $250,000 or less		657,615,000	718,256,000
Time Deposits, More than $250,000		181,016,000	197,064,000
Interest-bearing certificates	[1]	838,631,000	915,320,000
Total deposits		14,326,933,000	12,567,296,000
Included in total deposits:
Public fund transaction accounts		353,874,000	302,875,000
Public fund interest-bearing certificates		39,961,000	59,127,000
Total public deposits		393,835,000	362,002,000
Business Combination, Acquired Deposits, Time Deposit Premium		0	58,000
Related Party Deposit Liabilities		13,100,000	11,200,000
Time deposits equal to or greater than $250,000		$ 184,500,000	$ 203,600,000

[1] ) Certificates of deposit included no acquisition discounts at December 31, 2021 and $58,000 of acquisition discounts at December 31, 2020.