FAIR VALUE DISCLOSURES - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 28,657		$ 14,179
Financial assets
Investment securities held-to-maturity	628,497		726,259
Other investments	51,170		53,725
FDIC indemnification asset	13,287	$ 14,504	17,630	$ 18,931	$ 20,338	$ 22,666
Deposits
Noninterest-bearing	1,492,011		1,413,404
Savings	2,005,407		1,945,805
Time	1,346,736		1,406,124
Carrying value
Financial assets
Cash and short-term investments	134,747		148,575
Investment securities held-to-maturity	628,497		726,259
Other investments	51,170		53,725
Loans held for sale	17,414		20,957
Loans and leases, net of ALLL	5,731,893		5,335,362
FDIC indemnification asset	13,287		17,630
Interest Receivable	18,071		16,995
Deposits
Noninterest-bearing	1,492,011		1,413,404
Interest-bearing demand	1,494,529		1,414,291
Savings	2,005,407		1,945,805
Time	1,346,736		1,406,124
Total deposits	6,338,683		6,179,624
Short-term borrowings	926,236		938,425
Long-term debt	119,549		119,540
Interest Payable	3,523		5,003
Fair value
Financial assets
Cash and short-term investments	134,747		148,575
Investment securities held-to-maturity	645,751		731,951
Loans held for sale	17,414		20,957
Loans and leases, net of ALLL	5,787,327		5,381,065
FDIC indemnification asset	7,455		9,756
Interest Receivable	18,071		16,995
Deposits
Noninterest-bearing	1,492,011		1,413,404
Interest-bearing demand	1,494,529		1,414,291
Savings	2,005,407		1,945,805
Time	1,349,546		1,406,489
Total deposits	6,341,493		6,179,989
Short-term borrowings	926,236		938,425
Long-term debt	124,890		118,691
Interest Payable	3,523		5,003
Fair Value, Inputs, Level 1 [Member] | Fair value
Financial assets
Cash and short-term investments	134,747		148,575
Investment securities held-to-maturity	0		0
Loans held for sale	0		0
Loans and leases, net of ALLL	0		0
FDIC indemnification asset	0		0
Interest Receivable	0		0
Deposits
Noninterest-bearing	0		0
Interest-bearing demand	0		0
Savings	0		0
Time	0		0
Total deposits	0		0
Short-term borrowings	926,236		938,425
Long-term debt	0		0
Interest Payable	640		113
Fair Value, Inputs, Level 2 [Member] | Fair value
Financial assets
Cash and short-term investments	0		0
Investment securities held-to-maturity	645,751		731,951
Loans held for sale	17,414		20,957
Loans and leases, net of ALLL	0		0
FDIC indemnification asset	0		0
Interest Receivable	5,423		5,791
Deposits
Noninterest-bearing	1,492,011		1,413,404
Interest-bearing demand	1,494,529		1,414,291
Savings	2,005,407		1,945,805
Time	1,349,546		1,406,489
Total deposits	6,341,493		6,179,989
Short-term borrowings	0		0
Long-term debt	124,890		118,691
Interest Payable	2,883		4,890
Fair Value, Inputs, Level 3 [Member] | Fair value
Financial assets
Cash and short-term investments	0		0
Investment securities held-to-maturity	0		0
Loans held for sale	0		0
Loans and leases, net of ALLL	5,787,327		5,381,065
FDIC indemnification asset	7,455		9,756
Interest Receivable	12,648		11,204
Deposits
Noninterest-bearing	0		0
Interest-bearing demand	0		0
Savings	0		0
Time	0		0
Total deposits	0		0
Short-term borrowings	0		0
Long-term debt	0		0
Interest Payable	$ 0		$ 0