COMMITMENTS AND CONTINGENCIES - Loan and Unfunded Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Unused Commitments to Extend Credit	$ 3,090,331	$ 2,853,059
Loans and Leases Receivable, Net of Deferred Income	9,360,931	9,900,970
Commercial
Other Commitments [Line Items]
Unused Commitments to Extend Credit	1,418,937	1,270,765
Loans and Leases Receivable, Net of Deferred Income	2,602,848	3,007,509
Lease financing
Other Commitments [Line Items]
Unused Commitments to Extend Credit	18,229	0
Loans and Leases Receivable, Net of Deferred Income	67,855	72,987
Construction real estate
Other Commitments [Line Items]
Unused Commitments to Extend Credit	386,329	374,008
Loans and Leases Receivable, Net of Deferred Income	477,004	636,096
Commercial real estate - investor
Other Commitments [Line Items]
Unused Commitments to Extend Credit	129,332	139,754
Loans and Leases Receivable, Net of Deferred Income	3,399,664	3,244,540
Commercial real estate-owner
Other Commitments [Line Items]
Unused Commitments to Extend Credit	34,674	51,637
Loans and Leases Receivable, Net of Deferred Income	1,038,710	1,063,318
Residential real estate
Other Commitments [Line Items]
Unused Commitments to Extend Credit	53,055	28,895
Loans and Leases Receivable, Net of Deferred Income	922,492	1,003,086
Home equity
Other Commitments [Line Items]
Unused Commitments to Extend Credit	813,862	762,406
Loans and Leases Receivable, Net of Deferred Income	709,050	743,099
Installment
Other Commitments [Line Items]
Unused Commitments to Extend Credit	14,603	18,229
Loans and Leases Receivable, Net of Deferred Income	96,077	81,850
Credit card
Other Commitments [Line Items]
Unused Commitments to Extend Credit	221,310	207,365
Loans and Leases Receivable, Net of Deferred Income	$ 47,231	$ 48,485