LOANS AND ALLOWANCE FOR LOAN LOSSES (Impairment Method by Loan Category) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	$ 3,468		$ 2,237
Ending balance: Impaired loans collectively evaluated for impairment	5,226		10,234
Ending balance: All other loans collectively evaluated for impairment	51,075		54,403
Balance, end of period	59,769	$ 58,816	66,874	$ 74,694	$ 78,018	$ 81,033
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	47,296		37,541
Ending balance: Impaired loans collectively evaluated for impairment	53,680		100,554
Ending balance: All other loans collectively evaluated for impairment	3,295,538		2,979,737
Total loans held for portfolio	3,396,514		3,117,832
Commercial and Industrial [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0		1,053
Ending balance: Impaired loans collectively evaluated for impairment	336		573
Ending balance: All other loans collectively evaluated for impairment	10,653		10,948
Balance, end of period	10,989	11,321	12,574	13,859	13,731	13,401
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	2,210		4,712
Ending balance: Impaired loans collectively evaluated for impairment	3,192		5,058
Ending balance: All other loans collectively evaluated for impairment	741,742		685,497
Total loans held for portfolio	747,144		695,267
Real Estate Construction and Development [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0		0
Ending balance: Impaired loans collectively evaluated for impairment	200		219
Ending balance: All other loans collectively evaluated for impairment	2,167		3,271
Balance, end of period	2,367	2,231	3,490	2,733	6,600	7,407
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	2,615		2,626
Ending balance: Impaired loans collectively evaluated for impairment	599		1,109
Ending balance: All other loans collectively evaluated for impairment	145,334		86,116
Total loans held for portfolio	148,548		89,851
One-to-Four-Family Residential [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	3,468		1,184
Ending balance: Impaired loans collectively evaluated for impairment	4,400		7,821
Ending balance: All other loans collectively evaluated for impairment	13,143		15,050
Balance, end of period	21,011	22,403	24,055	29,102	29,145	32,619
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	39,901		7,388
Ending balance: Impaired loans collectively evaluated for impairment	47,791		89,561
Ending balance: All other loans collectively evaluated for impairment	1,014,382		919,761
Total loans held for portfolio	1,102,074		1,016,710
Multi-family residential [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0		0
Ending balance: Impaired loans collectively evaluated for impairment	18		1,157
Ending balance: All other loans collectively evaluated for impairment	3,357		4,473
Balance, end of period	3,375	3,430	5,630	7,757	7,374	5,249
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	0		19,050
Ending balance: Impaired loans collectively evaluated for impairment	290		681
Ending balance: All other loans collectively evaluated for impairment	93,987		95,703
Total loans held for portfolio	94,277		115,434
Commercial Real Estate [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0		0
Ending balance: Impaired loans collectively evaluated for impairment	271		463
Ending balance: All other loans collectively evaluated for impairment	21,682		20,520
Balance, end of period	21,953	19,349	20,983	20,915	20,820	22,052
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	2,570		3,765
Ending balance: Impaired loans collectively evaluated for impairment	1,791		4,122
Ending balance: All other loans collectively evaluated for impairment	1,282,404		1,175,155
Total loans held for portfolio	1,286,765		1,183,042
Consumer and Installment and Net Deferred Loan Fees [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0		0
Ending balance: Impaired loans collectively evaluated for impairment	1		1
Ending balance: All other loans collectively evaluated for impairment	73		141
Balance, end of period	74	$ 82	142	$ 328	$ 348	$ 305
Total loans:
Ending balance: Impaired loans individually evaluated for impairment	0		0
Ending balance: Impaired loans collectively evaluated for impairment	17		23
Ending balance: All other loans collectively evaluated for impairment	17,689		17,505
Total loans held for portfolio	$ 17,706		$ 17,528