FAIR VALUE - Summary of Carrying Value and Fair Value of Company's Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity		$ 379,657	$ 372,498
Loans, net		2,949,197	2,856,136
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	[1]	0	0
Loans, net		0	0
Deposit liabilities		0	0
Subordinated debt		0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	[1]	378,232	369,881
Loans, net		0	0
Deposit liabilities		0	0
Subordinated debt		54,963	54,908
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	[1]	0	0
Loans, net		2,928,227	2,840,993
Deposit liabilities		3,677,121	3,523,322
Subordinated debt		0	0
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity	[1]	379,657	372,498
Loans, net		2,940,728	2,852,016
Deposit liabilities		3,678,645	3,523,245
Subordinated debt		$ 70,311	$ 70,241

[1] See Note D for further detail of fair value of individual investment categories.