FAIR VALUE (Fair value measurement recurring) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Equity securities with a readily determinable fair value	$ 19,569
Level 1
Assets
Securities available for sale	2,035	$ 8,503
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 2
Assets
Securities available for sale	4,948,663	3,304,293
Derivative assets	50,387	17,527
Liabilities
Derivative liabilities	59,328	21,462
Level 3
Assets
Securities available for sale	0	0
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Forward commitments \| Level 1
Assets
Derivative assets	0
Forward commitments \| Level 2
Assets
Derivative assets	27
Forward commitments \| Level 3
Assets
Derivative assets	0
U.S. government corporations and agencies
Assets
Securities available for sale	3,272	9,893
Mortgage and asset-backed securities
Assets
Securities available for sale	3,742,508	2,577,278
Obligations of states and political subdivisions
Assets
Securities available for sale	1,185,349	707,190
Recurring Basis
Assets
Equity securities with a readily determinable fair value	19,569	18,435
Total assets at fair value	5,003,367	3,331,019
Liabilities
Total liabilities at fair value	59,680	21,575
Recurring Basis \| Level 1
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	2,035	8,503
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Level 2
Assets
Equity securities with a readily determinable fair value	19,569	18,435
Total assets at fair value	4,999,077	3,321,835
Liabilities
Total liabilities at fair value	59,680	21,575
Recurring Basis \| Level 3
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	2,255	681
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Derivative financial instruments
Assets
Derivative assets	50,387	17,527
Liabilities
Derivative liabilities	59,328	21,462
Recurring Basis \| Derivative financial instruments \| Level 1
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Derivative financial instruments \| Level 2
Assets
Derivative assets	50,387	17,527
Liabilities
Derivative liabilities	59,328	21,462
Recurring Basis \| Derivative financial instruments \| Level 3
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Interest rate lock commitments
Assets
Derivative assets	2,255	681
Recurring Basis \| Interest rate lock commitments \| Level 1
Assets
Derivative assets	0	0
Recurring Basis \| Interest rate lock commitments \| Level 2
Assets
Derivative assets	0	0
Recurring Basis \| Interest rate lock commitments \| Level 3
Assets
Derivative assets	2,255	681
Recurring Basis \| Forward commitments
Assets
Derivative assets	27
Liabilities
Derivative liabilities	352	113
Recurring Basis \| Forward commitments \| Level 1
Assets
Derivative assets	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Forward commitments \| Level 2
Assets
Derivative assets	27
Liabilities
Derivative liabilities	352	113
Recurring Basis \| Forward commitments \| Level 3
Assets
Derivative assets	0
Liabilities
Derivative liabilities	0	0
Recurring Basis \| U.S. government corporations and agencies
Assets
Securities available for sale	3,272	9,893
Recurring Basis \| U.S. government corporations and agencies \| Level 1
Assets
Securities available for sale	2,035	8,503
Recurring Basis \| U.S. government corporations and agencies \| Level 2
Assets
Securities available for sale	1,237	1,390
Recurring Basis \| U.S. government corporations and agencies \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage and asset-backed securities
Assets
Securities available for sale	3,742,508	2,577,278
Recurring Basis \| Mortgage and asset-backed securities \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Mortgage and asset-backed securities \| Level 2
Assets
Securities available for sale	3,742,508	2,577,278
Recurring Basis \| Mortgage and asset-backed securities \| Level 3
Assets
Securities available for sale	0	0
Recurring Basis \| Obligations of states and political subdivisions
Assets
Securities available for sale	1,185,349	707,190
Recurring Basis \| Obligations of states and political subdivisions \| Level 1
Assets
Securities available for sale	0	0
Recurring Basis \| Obligations of states and political subdivisions \| Level 2
Assets
Securities available for sale	1,185,349	707,190
Recurring Basis \| Obligations of states and political subdivisions \| Level 3
Assets
Securities available for sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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