LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Impaired Loans With and Without Specific Reserves) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ (52,293)		$ (45,891)
Unpaid Principal Balance	56,994		49,319
Allowance collectively evaluated for impairment	72,759				69,678
Related Allowance	2,836		3,092
Loans collectively evaluated for impairment	4,069,059				3,469,903
Average Recorded Investment	46,927		45,440
Interest Income Recognized	363		1,528
Loans individually evaluated for impairment	40,085				53,009
Allowance on loans individually evaluated for impairment	2,606				4,693
Commerical real estate - owner-occupied [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(3,917)		(1,548)
Unpaid Principal Balance	3,967		1,598
Related Allowance	37		24
Average Recorded Investment	2,698		1,841
Interest Income Recognized	3		12
Commerical real estate - investment properties [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(6,388)		(6,054)
Unpaid Principal Balance	6,793		6,458
Related Allowance	707		729
Average Recorded Investment	6,490		6,145
Interest Income Recognized	77		315
Multifamily real estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,359)		(786)
Unpaid Principal Balance	1,359		786
Allowance collectively evaluated for impairment	4,317				4,593
Related Allowance	84		86
Loans collectively evaluated for impairment	207,328				147,277
Average Recorded Investment	975		795
Interest Income Recognized	11		45
Loans individually evaluated for impairment	1,359				5,726
Allowance on loans individually evaluated for impairment	84				1,059
One-to four-family construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(4,160)		(3,923)
Unpaid Principal Balance	4,197		3,923
Related Allowance	454		640
Average Recorded Investment	3,097		2,655
Interest Income Recognized	31		118
Land and land development - residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(2,543)		(2,554)
Unpaid Principal Balance	3,698		3,710
Related Allowance	354		346
Average Recorded Investment	2,547		2,872
Interest Income Recognized	16		89
Land and land development - commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(4,870)
Unpaid Principal Balance	5,445
Related Allowance	0
Average Recorded Investment	1,624
Interest Income Recognized	0
Commercial business [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,143)		(1,276)
Unpaid Principal Balance	1,356		1,502
Allowance collectively evaluated for impairment	12,814				11,204
Related Allowance	122		128
Loans collectively evaluated for impairment	775,854				715,506
Average Recorded Investment	1,172		1,328
Interest Income Recognized	9		41
Loans individually evaluated for impairment	725				1,040
Allowance on loans individually evaluated for impairment	78				159
Agricultural business, including secured by farmland [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,855)		(1,597)
Unpaid Principal Balance	2,481		1,597
Allowance collectively evaluated for impairment	3,729				2,636
Related Allowance	69		26
Loans collectively evaluated for impairment	208,346				208,817
Average Recorded Investment	2,317		1,866
Interest Income Recognized	5		0
Loans individually evaluated for impairment	289				0
Allowance on loans individually evaluated for impairment	3				0
One- to four-family residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(23,786)		(26,394)
Unpaid Principal Balance	25,206		27,855
Allowance collectively evaluated for impairment	7,216				9,621
Related Allowance	941		1,032
Loans collectively evaluated for impairment	535,295				492,662
Average Recorded Investment	24,025		26,093
Interest Income Recognized	204		870
Loans individually evaluated for impairment	16,036				24,959
Allowance on loans individually evaluated for impairment	925				1,292
Consumer secured by one- to four-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,189)		(1,151)
Unpaid Principal Balance	1,264		1,256
Related Allowance	62		75
Average Recorded Investment	1,209		1,248
Interest Income Recognized	3		19
Consumer - other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,083)		(608)
Unpaid Principal Balance	1,228		634
Related Allowance	6		6
Average Recorded Investment	773		597
Interest Income Recognized	4		19
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(12,208)	[1]	(11,445)	[1]
Unpaid Principal Balance	13,839	[1]	12,534	[1]
Related Allowance	229	[1]	126	[1]
Average Recorded Investment	12,829	[1]	10,650	[1]
Interest Income Recognized	6	[1]	32	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Commerical real estate - owner-occupied [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(940)	[1]	(399)	[1]
Unpaid Principal Balance	990	[1]	449	[1]
Related Allowance	34	[1]	20	[1]
Average Recorded Investment	946	[1]	526	[1]
Interest Income Recognized	0	[1]	0	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Commerical real estate - investment properties [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(407)	[1]	(32)	[1]
Unpaid Principal Balance	407	[1]	32	[1]
Related Allowance	66	[1]	5	[1]
Average Recorded Investment	495	[1]	44	[1]
Interest Income Recognized	0	[1]	0	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Commercial business [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(418)	[1]	(537)	[1]
Unpaid Principal Balance	631	[1]	763	[1]
Related Allowance	44	[1]	46	[1]
Average Recorded Investment	443	[1]	566	[1]
Interest Income Recognized	0	[1]	0	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,566)	[1]	(853)	[1]
Unpaid Principal Balance	2,192	[1]	853	[1]
Related Allowance	66	[1]	26	[1]
Average Recorded Investment	2,032	[1]	1,122	[1]
Interest Income Recognized	0	[1]	0	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | One- to four-family residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(7,750)	[1]	(8,546)	[1]
Unpaid Principal Balance	8,407	[1]	9,244	[1]
Related Allowance	16	[1]	18	[1]
Average Recorded Investment	7,764	[1]	7,284	[1]
Interest Income Recognized	6	[1]	29	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Consumer secured by one- to four-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(824)	[1]	(783)	[1]
Unpaid Principal Balance	899	[1]	888	[1]
Related Allowance	3	[1]	11	[1]
Average Recorded Investment	842	[1]	838	[1]
Interest Income Recognized	0	[1]	3	[1]
Loans Without Specific Allowance Reserve, Collectively Evaluated for Impairment [Member] | Consumer - other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(303)	[1]	(295)	[1]
Unpaid Principal Balance	313	[1]	305	[1]
Related Allowance	0	[1]	0	[1]
Average Recorded Investment	307	[1]	270	[1]
Interest Income Recognized	0	[1]	0	[1]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(40,085)	[2]	(34,446)	[2]
Unpaid Principal Balance	43,155	[2]	36,785	[2]
Related Allowance	2,607	[2]	2,966	[2]
Average Recorded Investment	34,098	[2]	34,790	[2]
Interest Income Recognized	357	[2]	1,496	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Commerical real estate - owner-occupied [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(2,977)	[2]	(1,149)	[2]
Unpaid Principal Balance	2,977	[2]	1,149	[2]
Related Allowance	3	[2]	4	[2]
Average Recorded Investment	1,752	[2]	1,315	[2]
Interest Income Recognized	3	[2]	12	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Commerical real estate - investment properties [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(5,981)	[2]	(6,022)	[2]
Unpaid Principal Balance	6,386	[2]	6,426	[2]
Related Allowance	641	[2]	724	[2]
Average Recorded Investment	5,995	[2]	6,101	[2]
Interest Income Recognized	77	[2]	315	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Multifamily real estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(1,359)	[2]	(786)	[2]
Unpaid Principal Balance	1,359	[2]	786	[2]
Related Allowance	84	[2]	86	[2]
Average Recorded Investment	975	[2]	795	[2]
Interest Income Recognized	11	[2]	45	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | One-to four-family construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(4,160)	[2]	(3,923)	[2]
Unpaid Principal Balance	4,197	[2]	3,923	[2]
Related Allowance	454	[2]	640	[2]
Average Recorded Investment	3,097	[2]	2,655	[2]
Interest Income Recognized	31	[2]	118	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Land and land development - residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(2,543)	[2]	(2,554)	[2]
Unpaid Principal Balance	3,698	[2]	3,710	[2]
Related Allowance	354	[2]	346	[2]
Average Recorded Investment	2,547	[2]	2,872	[2]
Interest Income Recognized	16	[2]	89	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Land and land development - commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(4,870)
Unpaid Principal Balance	5,445
Related Allowance	0
Average Recorded Investment	1,624
Interest Income Recognized	0
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Commercial business [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(725)	[2]	(739)	[2]
Unpaid Principal Balance	725	[2]	739	[2]
Related Allowance	78	[2]	82	[2]
Average Recorded Investment	729	[2]	762	[2]
Interest Income Recognized	9	[2]	41	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(289)		(744)
Unpaid Principal Balance	289		744
Related Allowance	3		0
Average Recorded Investment	285		744
Interest Income Recognized	5		0
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | One- to four-family residential [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(16,036)	[2]	(17,848)	[2]
Unpaid Principal Balance	16,799	[2]	18,611	[2]
Related Allowance	925	[2]	1,014
Average Recorded Investment	16,261	[2]	18,809	[2]
Interest Income Recognized	198	[2]	841	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Consumer secured by one- to four-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(365)	[2]	(368)	[2]
Unpaid Principal Balance	365	[2]	368	[2]
Related Allowance	59	[2]	64	[2]
Average Recorded Investment	367	[2]	410	[2]
Interest Income Recognized	3	[2]	16	[2]
With Specific Allowance Reserve , Individually Evaluated for Impairment [Member] | Consumer - other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	(780)	[2]	(313)	[2]
Unpaid Principal Balance	915	[2]	329	[2]
Related Allowance	6	[2]	6	[2]
Average Recorded Investment	466	[2]	327	[2]
Interest Income Recognized	$ 4	[2]	$ 19	[2]

[1] Loans without a specific allowance reserve have not been individually evaluated for impairment, but have been included in pools of homogeneous loans for evaluation of related allowance reserves.

[2] Loans with a specific allowance reserve have been individually evaluated for impairment using either a discounted cash flow analysis or, for collateral dependent loans, current appraisals less costs to sell to establish realizable value. These analyses may identify a specific impairment amount needed or may conclude that no reserve is needed. Any specific impairment that is identified is included in the category’s Related Allowance column.