LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Age Analysis of Company's Past Due Loans) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	$ 3,011	$ 7,886
60 to 89 Days Past Due	5,827	7,930
Greater Than 90 Days Past Due	21,535	53,401
Total Past Due	30,373	69,217
Current	3,183,150	3,227,121
Total loans outstanding	3,213,523	3,296,338	3,225,246
Loans 90 Days or More Past Due and Accruing	2,078	2,324
Commerical real estate - owner-occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	846	1,251
60 to 89 Days Past Due	1,684	2,703
Greater Than 90 Days Past Due	938	3,462
Total Past Due	3,468	7,416
Current	474,403	462,390
Total loans outstanding	477,871	469,806	474,863
Loans 90 Days or More Past Due and Accruing	0	0
Commerical real estate - investment properties [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	0
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	1,418	3,087
Total Past Due	1,418	3,087
Current	602,847	618,535
Total loans outstanding	604,265	621,622	586,652
Loans 90 Days or More Past Due and Accruing	0	0
Multifamily real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	0
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	0	0
Current	138,716	139,710
Total loans outstanding	138,716	139,710	134,146
Loans 90 Days or More Past Due and Accruing	0	0
Commercial construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	0
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	949
Total Past Due	0	949
Current	28,598	41,442
Total loans outstanding	28,598	42,391	38,124
Loans 90 Days or More Past Due and Accruing	0	0
Multifamily construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	0
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	0	0
Current	14,502	19,436
Total loans outstanding	14,502	19,436	16,335
Loans 90 Days or More Past Due and Accruing	0	0
One-to four-family construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	643
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	243	3,819
Total Past Due	243	4,462
Current	163,278	139,715
Total loans outstanding	163,521	144,177	145,776
Loans 90 Days or More Past Due and Accruing	0	0
Land and land development - residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	638
60 to 89 Days Past Due	389	0
Greater Than 90 Days Past Due	3,630	15,919
Total Past Due	4,019	16,557
Current	75,913	80,934
Total loans outstanding	79,932	97,491	96,875
Loans 90 Days or More Past Due and Accruing	0	0
Land and land development - commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	0	308
60 to 89 Days Past Due	46	0
Greater Than 90 Days Past Due	445	791
Total Past Due	491	1,099
Current	13,751	14,098
Total loans outstanding	14,242	15,197	19,173
Loans 90 Days or More Past Due and Accruing	0	0
Commercial business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	273	2,411
60 to 89 Days Past Due	391	4,170
Greater Than 90 Days Past Due	2,226	5,612
Total Past Due	2,890	12,193
Current	600,716	589,247
Total loans outstanding	603,606	601,440	580,876
Loans 90 Days or More Past Due and Accruing	15	4
Agricultural business, including secured by farming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	22	99
60 to 89 Days Past Due	0	0
Greater Than 90 Days Past Due	626	1,849
Total Past Due	648	1,948
Current	218,436	216,223
Total loans outstanding	219,084	218,171	211,571
Loans 90 Days or More Past Due and Accruing	0	0
One- to four-family real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	1,098	794
60 to 89 Days Past Due	2,171	585
Greater Than 90 Days Past Due	10,566	15,770
Total Past Due	13,835	17,149
Current	580,578	625,352
Total loans outstanding	594,413	642,501	639,909
Loans 90 Days or More Past Due and Accruing	2,037	2,147
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	448	670
60 to 89 Days Past Due	72	363
Greater Than 90 Days Past Due	195	769
Total Past Due	715	1,802
Current	102,678	101,545
Total loans outstanding	103,393	103,347	98,794
Loans 90 Days or More Past Due and Accruing	21	25
Consumer secured by one- to four-family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 to 59 Days Past Due	324	1,072
60 to 89 Days Past Due	1,074	109
Greater Than 90 Days Past Due	1,248	1,374
Total Past Due	2,646	2,555
Current	168,734	178,494
Total loans outstanding	171,380	181,049	182,152
Loans 90 Days or More Past Due and Accruing	$ 5	$ 148