LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Allowance for Loan Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	$ 77,329	$ 74,310	$ 75,907	$ 74,258
PROVISION FOR LOAN LOSSES	0	0	0	0
Recoveries	1,064	1,217	4,913	4,463
Charge-offs	(1,073)	(1,196)	(3,500)	(4,390)
Allowance for loan losses, Ending balance	77,320	74,331	77,320	74,331
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					$ 2,015		$ 3,419
Allowance collectively evaluated for impairment					75,305		70,912
Total allowance for loan losses	77,329	74,310	75,907	74,258	77,320	$ 75,907	74,331
Loans individually evaluated for impairment					28,477		35,923
Loans collectively evaluated for impairment					4,338,708		3,770,772
Total loans					4,372,594	3,833,820	3,806,695
Commercial real estate [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	18,948	18,884	18,784	16,759
PROVISION FOR LOAN LOSSES	317	527	333	3,321
Recoveries	375	94	587	664
Charge-offs	0	0	(64)	(1,239)
Allowance for loan losses, Ending balance	19,640	19,505	19,640	19,505
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					612		755
Allowance collectively evaluated for impairment					19,028		18,750
Total allowance for loan losses	18,948	18,884	18,784	16,759	19,640	18,784	19,505
Loans individually evaluated for impairment					6,182		8,070
Loans collectively evaluated for impairment					1,690,251		1,392,547
Total loans					1,697,564	1,403,725	1,400,617
Multifamily real estate [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	4,273	5,765	4,562	5,306
PROVISION FOR LOAN LOSSES	90	(853)	(312)	(394)
Recoveries	0	0	113	0
Charge-offs	0	(20)	0	(20)
Allowance for loan losses, Ending balance	4,363	4,892	4,363	4,892
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					73		91
Allowance collectively evaluated for impairment					4,290		4,801
Total allowance for loan losses	4,273	5,765	4,562	5,306	4,363	4,562	4,892
Loans individually evaluated for impairment					361		791
Loans collectively evaluated for impairment					198,072		183,153
Total loans					198,874	167,524	183,944
Construction and Land [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	25,415	17,837	23,545	17,640
PROVISION FOR LOAN LOSSES	1,929	2,858	2,847	2,558
Recoveries	282	84	1,234	788
Charge-offs	(352)	0	(352)	(207)
Allowance for loan losses, Ending balance	27,274	20,779	27,274	20,779
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					473		1,269
Allowance collectively evaluated for impairment					26,801		19,510
Total allowance for loan losses	25,415	17,837	23,545	17,640	27,274	23,545	20,779
Loans individually evaluated for impairment					6,034		6,643
Loans collectively evaluated for impairment					484,241		374,864
Total loans					493,800	411,006	381,507
Commercial business [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	13,184	12,014	12,043	11,773
PROVISION FOR LOAN LOSSES	(235)	490	664	1,150
Recoveries	128	256	803	835
Charge-offs	(312)	(83)	(745)	(1,081)
Allowance for loan losses, Ending balance	12,765	12,677	12,765	12,677
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					74		103
Allowance collectively evaluated for impairment					12,691		12,574
Total allowance for loan losses	13,184	12,014	12,043	11,773	12,765	12,043	12,677
Loans individually evaluated for impairment					644		880
Loans collectively evaluated for impairment					811,426		727,208
Total loans					812,070	723,964	728,088
Agricultural Business/Farmland [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	2,679	2,824	2,821	2,841
PROVISION FOR LOAN LOSSES	(292)	(339)	(890)	(1,017)
Recoveries	146	587	1,666	1,248
Charge-offs	0	(125)	(1,064)	(125)
Allowance for loan losses, Ending balance	2,533	2,947	2,533	2,947
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					17		0
Allowance collectively evaluated for impairment					2,516		2,947
Total allowance for loan losses	2,679	2,824	2,821	2,841	2,533	2,821	2,947
Loans individually evaluated for impairment					776		0
Loans collectively evaluated for impairment					241,780		240,048
Total loans					242,556	238,499	240,048
One- to four-family [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	8,542	9,270	8,447	11,486
PROVISION FOR LOAN LOSSES	(635)	(38)	(524)	(2,253)
Recoveries	42	143	141	535
Charge-offs	(12)	(239)	(127)	(632)
Allowance for loan losses, Ending balance	7,937	9,136	7,937	9,136
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					706		1,143
Allowance collectively evaluated for impairment					7,231		7,993
Total allowance for loan losses	8,542	9,270	8,447	11,486	7,937	8,447	9,136
Loans individually evaluated for impairment					13,952		18,890
Loans collectively evaluated for impairment					522,373		508,381
Total loans					536,325	539,894	527,271
Consumer [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	780	748	483	1,335
PROVISION FOR LOAN LOSSES	330	603	1,100	33
Recoveries	91	53	369	393
Charge-offs	(397)	(729)	(1,148)	(1,086)
Allowance for loan losses, Ending balance	804	675	804	675
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					60		58
Allowance collectively evaluated for impairment					744		617
Total allowance for loan losses	780	748	483	1,335	804	483	675
Loans individually evaluated for impairment					528		649
Loans collectively evaluated for impairment					390,565		344,571
Total loans					391,405	349,208	345,220
Unallocated Financing Receivables [Member]
Financing Receivable, Allowance for Loan Losses [Roll Forward]
Allowance for loan losses, Beginning balance	3,508	6,968	5,222	7,118
PROVISION FOR LOAN LOSSES	(1,504)	(3,248)	(3,218)	(3,398)
Recoveries	0	0	0	0
Charge-offs	0	0	0	0
Allowance for loan losses, Ending balance	2,004	3,720	2,004	3,720
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Allowance individually evaluated for impairment					0		0
Allowance collectively evaluated for impairment					2,004		3,720
Total allowance for loan losses	$ 3,508	$ 6,968	$ 5,222	$ 7,118	2,004	$ 5,222	3,720
Loans individually evaluated for impairment					0		0
Loans collectively evaluated for impairment					0		0
Total loans					0		$ 0
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					5,409
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial real estate [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					1,131
Receivables Acquired with Deteriorated Credit Quality [Member] | Multifamily real estate [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					441
Receivables Acquired with Deteriorated Credit Quality [Member] | Construction and Land [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					3,525
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial business [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					0
Receivables Acquired with Deteriorated Credit Quality [Member] | Agricultural Business/Farmland [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					0
Receivables Acquired with Deteriorated Credit Quality [Member] | One- to four-family [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					312
Receivables Acquired with Deteriorated Credit Quality [Member] | Unallocated Financing Receivables [Member]
Financing Receivable, Allowance for Loan Losses, Additional Information [Abstract]
Total loans					$ 0