FAIR VALUE - Summary of Carrying Value and Fair Value of Company's Financial Instruments (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities held to maturity		$ 397,096	$ 372,498
Loans, net		3,304,075	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
Time deposits with other banks		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]	397,357	369,881
Time deposits with other banks		0
Loans, net		0	0
Deposit liabilities		0	0
Subordinated debt		55,017	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
Time deposits with other banks		16,386
Loans, net		3,277,109	2,840,993
Deposit liabilities		3,973,456	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]	397,096	372,498
Time deposits with other banks		16,426
Loans, net		3,293,365	2,852,016
Deposit liabilities		3,975,458	3,523,245
Subordinated debt		$ 70,381	$ 70,241

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