LOANS AND ALLOWANCE FOR LOAN LOSSES (Impairment Method by Loan Category) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	$ 2,237	$ 3,756
Ending balance: Impaired loans collectively evaluated for impairment	10,234	11,675
Ending balance: All other loans collectively evaluated for impairment	54,403	65,602
Balance, end of period	66,874	81,033	91,602	137,710
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	37,541	57,005
Ending balance: Impaired loans collectively evaluated for impairment	100,554	106,578
Ending balance: All other loans collectively evaluated for impairment	2,979,737	2,667,964
Ending balance	3,117,832	2,831,547
Commercial and Industrial [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	1,053	0
Ending balance: Impaired loans collectively evaluated for impairment	573	497
Ending balance: All other loans collectively evaluated for impairment	10,948	12,904
Balance, end of period	12,574	13,401	13,572
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	4,712	3,480
Ending balance: Impaired loans collectively evaluated for impairment	5,058	7,043
Ending balance: All other loans collectively evaluated for impairment	685,497	590,181
Ending balance	695,267	600,704
Real Estate Construction and Development [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0	62
Ending balance: Impaired loans collectively evaluated for impairment	219	232
Ending balance: All other loans collectively evaluated for impairment	3,271	7,113
Balance, end of period	3,490	7,407	14,434
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	2,626	3,440
Ending balance: Impaired loans collectively evaluated for impairment	1,109	1,474
Ending balance: All other loans collectively evaluated for impairment	86,116	116,748
Ending balance	89,851	121,662
One-to-Four-Family Residential [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	1,184	2,275
Ending balance: Impaired loans collectively evaluated for impairment	7,821	8,937
Ending balance: All other loans collectively evaluated for impairment	15,050	21,407
Balance, end of period	24,055	32,619	38,897
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	7,388	12,276
Ending balance: Impaired loans collectively evaluated for impairment	89,561	93,301
Ending balance: All other loans collectively evaluated for impairment	919,761	815,911
Ending balance	1,016,710	921,488
Multi-family residential [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0	1,034
Ending balance: Impaired loans collectively evaluated for impairment	1,157	1,404
Ending balance: All other loans collectively evaluated for impairment	4,473	2,811
Balance, end of period	5,630	5,249	4,252
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	19,050	28,641
Ending balance: Impaired loans collectively evaluated for impairment	681	1,107
Ending balance: All other loans collectively evaluated for impairment	95,703	91,556
Ending balance	115,434	121,304
Commercial Real Estate [Member]
Allowance for loan losses:
Ending balance: Impaired loans individually evaluated for impairment	0	385
Ending balance: Impaired loans collectively evaluated for impairment	463	605
Ending balance: All other loans collectively evaluated for impairment	20,520	21,062
Balance, end of period	20,983	22,052	20,048
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	3,765	9,168
Ending balance: Impaired loans collectively evaluated for impairment	4,122	3,634
Ending balance: All other loans collectively evaluated for impairment	1,175,155	1,035,432
Ending balance	1,183,042	1,048,234
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	0
Ending balance: All other loans collectively evaluated for impairment	141	305
Balance, end of period	142	305	399
Total Loans:
Ending balance: Impaired loans individually evaluated for impairment	0	0
Ending balance: Impaired loans collectively evaluated for impairment	23	19
Ending balance: All other loans collectively evaluated for impairment	17,505	18,136
Ending balance	$ 17,528	$ 18,155