INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investment Holdings [Line Items]
Total	$ 669,816	$ 763,254
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	6,872	6,236
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(4,452)	(5,915)
Held-to-Maturity Market Value	672,236	763,575
Total	1,281,320	1,045,337
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	10,201	4,716
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(4,751)	(10,183)
Investment securities available-for-sale	1,286,770	1,039,870
U.S. Treasuries
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	98	98
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	(1)
Investment securities available-for-sale	98	97
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	11,588	13,011
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	33	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(23)	(110)
Held-to-Maturity Market Value	11,598	12,901
Total	16,284	7,056
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	224	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	(40)
Investment securities available-for-sale	16,508	7,016
Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	171,468	205,522
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	2,066	1,740
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(1,219)	(1,166)
Held-to-Maturity Market Value	172,315	206,096
Total	272,254	184,960
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,471	1,175
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,609)	(2,740)
Investment securities available-for-sale	272,116	183,395
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	257,590	278,728
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	2,655	3,254
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(2,053)	(1,817)
Held-to-Maturity Market Value	258,192	280,165
Total	142,152	154,239
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	567	188
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(521)	(826)
Investment securities available-for-sale	142,198	153,601
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	153,806	195,408
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	934	1,125
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(915)	(1,476)
Held-to-Maturity Market Value	153,825	195,057
Total	304,679	232,701
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,551	634
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,127)	(2,321)
Investment securities available-for-sale	305,103	231,014
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	75,364	70,585
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	1,184	117
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(242)	(1,346)
Held-to-Maturity Market Value	76,306	69,356
Total	127,122	96,934
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,556	1,461
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(701)	(1,514)
Investment securities available-for-sale	128,977	96,881
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	340,477	322,708
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,921	517
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(517)	(2,013)
Investment securities available-for-sale	341,881	321,212
Other securities
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	78,254	46,641
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,911	741
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(276)	(728)
Investment securities available-for-sale	$ 79,889	$ 46,654

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

+ Details

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

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

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

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.6)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

+ References

+ Details

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

- Definition

Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

+ References

+ Details

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

- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	invest_InvestmentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	invest_InvestmentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	invest_InvestmentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: