FAIR VALUE (Fair value measurement recurring) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
Securities available for sale	$ 2,400,460	$ 2,450,709
Equity securities with a readily determinable fair value	17,339
Level 1
Assets
Securities available for sale	20,458	25,414
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 2
Assets
Securities available for sale	2,380,002	2,425,295
Derivative assets	8,403	6,539
Liabilities
Derivative liabilities	10,858	6,044
Level 3
Assets
Securities available for sale	0	0
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Recurring Basis
Assets
Equity securities with a readily determinable fair value	17,339	17,086
Total assets at fair value	2,409,663	2,457,973
Liabilities
Total liabilities at fair value	11,140	6,443
Recurring Basis \| Level 1
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	20,458	25,414
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Level 2
Assets
Equity securities with a readily determinable fair value	17,339	17,086
Total assets at fair value	2,388,405	2,431,834
Liabilities
Total liabilities at fair value	11,140	6,443
Recurring Basis \| Level 3
Assets
Equity securities with a readily determinable fair value	0	0
Total assets at fair value	800	725
Liabilities
Total liabilities at fair value	0	0
Recurring Basis \| Derivative financial instruments
Assets
Derivative assets	8,403	6,539
Liabilities
Derivative liabilities	10,858	6,044
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	8,403	6,539
Liabilities
Derivative liabilities	10,858	6,044
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	800	725
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	800	725
Recurring Basis \| Forward commitments
Liabilities
Derivative liabilities	282	399
Recurring Basis \| Forward commitments \| Level 1
Liabilities
Derivative liabilities	0	0
Recurring Basis \| Forward commitments \| Level 2
Liabilities
Derivative liabilities	282	399
Recurring Basis \| Forward commitments \| Level 3
Liabilities
Derivative liabilities	0	0
Recurring Basis \| U.S. government corporations and agencies
Assets
Securities available for sale	26,768	31,951
Recurring Basis \| U.S. government corporations and agencies \| Level 1
Assets
Securities available for sale	20,458	25,414
Recurring Basis \| U.S. government corporations and agencies \| Level 2
Assets
Securities available for sale	6,310	6,537
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	1,871,398	2,026,698
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	1,871,398	2,026,698
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	484,955	374,974
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	484,955	374,974
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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

Name:	us-gaap_DerivativeAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

+ Details

Name:	us-gaap_DerivativeLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

+ Details

Name:	us-gaap_EquitySecuritiesFvNi
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: