FAIR VALUE (Fair value measurement recurring) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Equity securities with a readily determinable fair value	$ 20,790
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	1,013	$ 2,026
Derivative instruments	0	0
Liabilities
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	7,448,923	6,125,949
Derivative instruments	26,232	44,102
Liabilities
Derivative liabilities	27,782	51,962
Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Derivative instruments	0	0
Liabilities
Derivative liabilities	0	0
U.S. treasuries
Assets
Securities available for sale	1,013	2,026
U.S. agencies
Assets
Securities available for sale	35,033	166,779
Obligations of states and political subdivisions
Assets
Securities available for sale	1,823,465	1,635,227
Commercial mortgage-backed securities - agency
Assets
Securities available for sale	127,861	174,153
Commercial mortgage-backed securities - non-agency
Assets
Securities available for sale	561,667	252,767
Asset-backed securities
Assets
Securities available for sale	877,646	1,069,266
Corporate bonds
Assets
Securities available for sale	3,294	3,742
Recurring Basis
Assets
Equity securities with a readily determinable fair value	20,790	19,629
Total assets at fair value	7,477,650	6,173,904
Liabilities
Total liabilities at fair value	27,841	52,659
Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	1,013	2,026
Liabilities
Total liabilities at fair value	0	0
Recurring Basis | Significant Other Observable Inputs (Level 2)
Assets
Equity securities with a readily determinable fair value	20,790	19,629
Total assets at fair value	7,475,433	6,170,051
Liabilities
Total liabilities at fair value	27,841	52,659
Recurring Basis | Significant Unobservable Inputs (Level 3)
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	1,204	1,827
Liabilities
Total liabilities at fair value	0	0
Recurring Basis | Derivative financial instruments
Assets
Derivative instruments	26,232	44,102
Liabilities
Derivative liabilities	27,782	51,962
Recurring Basis | Derivative financial instruments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Derivative instruments	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis | Derivative financial instruments | Significant Other Observable Inputs (Level 2)
Assets
Derivative instruments	26,232	44,102
Liabilities
Derivative liabilities	27,782	51,962
Recurring Basis | Derivative financial instruments | Significant Unobservable Inputs (Level 3)
Assets
Derivative instruments	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis | Interest rate lock commitments
Assets
Derivative instruments	1,204	1,827
Recurring Basis | Interest rate lock commitments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Derivative instruments	0	0
Recurring Basis | Interest rate lock commitments | Significant Other Observable Inputs (Level 2)
Assets
Derivative instruments	0	0
Recurring Basis | Interest rate lock commitments | Significant Unobservable Inputs (Level 3)
Assets
Derivative instruments	1,204	1,827
Recurring Basis | Forward commitments
Assets
Derivative instruments	278
Liabilities
Derivative liabilities	59	697
Recurring Basis | Forward commitments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Derivative instruments	0
Liabilities
Derivative liabilities	0	0
Recurring Basis | Forward commitments | Significant Other Observable Inputs (Level 2)
Assets
Derivative instruments	278
Liabilities
Derivative liabilities	59	697
Recurring Basis | Forward commitments | Significant Unobservable Inputs (Level 3)
Assets
Derivative instruments	0
Liabilities
Derivative liabilities	0	0
Recurring Basis | U.S. treasuries
Assets
Securities available for sale	1,013	2,026
Recurring Basis | U.S. treasuries | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	1,013	2,026
Recurring Basis | U.S. treasuries | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	0	0
Recurring Basis | U.S. treasuries | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | U.S. agencies
Assets
Securities available for sale	35,033	166,779
Recurring Basis | U.S. agencies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | U.S. agencies | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	35,033	166,779
Recurring Basis | U.S. agencies | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Obligations of states and political subdivisions
Assets
Securities available for sale	1,823,465	1,635,227
Recurring Basis | Obligations of states and political subdivisions | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Obligations of states and political subdivisions | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	1,823,465	1,635,227
Recurring Basis | Obligations of states and political subdivisions | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Mortgage-backed securities - agency
Assets
Securities available for sale	2,371,264	1,355,270
Recurring Basis | Mortgage-backed securities - agency | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Mortgage-backed securities - agency | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	2,371,264	1,355,270
Recurring Basis | Mortgage-backed securities - agency | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Mortgage-backed securities - non-agency
Assets
Securities available for sale	1,627,903	1,449,116
Recurring Basis | Mortgage-backed securities - non-agency | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Mortgage-backed securities - non-agency | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	1,627,903	1,449,116
Recurring Basis | Mortgage-backed securities - non-agency | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Commercial mortgage-backed securities - agency
Assets
Securities available for sale	127,861	174,153
Recurring Basis | Commercial mortgage-backed securities - agency | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Commercial mortgage-backed securities - agency | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	127,861	174,153
Recurring Basis | Commercial mortgage-backed securities - agency | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Commercial mortgage-backed securities - non-agency
Assets
Securities available for sale	561,667	252,767
Recurring Basis | Commercial mortgage-backed securities - non-agency | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Commercial mortgage-backed securities - non-agency | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	561,667	252,767
Recurring Basis | Commercial mortgage-backed securities - non-agency | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Asset-backed securities
Assets
Securities available for sale	877,646	1,069,266
Recurring Basis | Asset-backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Asset-backed securities | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	877,646	1,069,266
Recurring Basis | Asset-backed securities | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	0	0
Recurring Basis | Corporate bonds
Assets
Securities available for sale	3,294	3,742
Recurring Basis | Corporate bonds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale	0	0
Recurring Basis | Corporate bonds | Significant Other Observable Inputs (Level 2)
Assets
Securities available for sale	3,294	3,742
Recurring Basis | Corporate bonds | Significant Unobservable Inputs (Level 3)
Assets
Securities available for sale	$ 0	$ 0