INCOME TAXES - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
Tax computed at statutory rate of 35%	$ 30,533	$ 24,718	$ 9,491
Effect of state income taxes, net of federal benefit	2,367	2,635	1,287
Change in state income tax rates	(327)	(361)	(1,899)
Non-taxable interest income	(1,329)	(828)	(437)
Non-taxable bank-owned life insurance	(1,423)	(655)	(549)
Non-deductible merger costs	1,819	94	1,006
Write-off of acquired net operating losses subject to Section 382 limitation	0	0	652
Change in deferred tax asset valuation allowance	(296)	(126)	(4,797)
Other	726	518	659
Income tax expense	$ 32,070	$ 25,995	$ 5,413