LOANS RECEIVABLE AND THE ALLOWANCE FOR LOAN LOSSES (Risk-Rate and Non-Risk Rated Loans by Grade and Other Characteristic) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	$ 3,235,714		$ 3,296,338
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	1,073,222		1,091,428
Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	137,504		139,710
Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	304,617		318,692
Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	618,049		601,440
Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	230,031		218,171
One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	581,670		642,501
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	290,621	[1]	284,396	[1]
Pass (Risk Ratings 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	3,077,933		3,034,355
Pass (Risk Ratings 1-5) [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	1,016,964		1,003,990
Pass (Risk Ratings 1-5) [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	130,815		132,108
Pass (Risk Ratings 1-5) [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	274,407		257,685
Pass (Risk Ratings 1-5) [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	581,846		542,625
Pass (Risk Ratings 1-5) [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	228,304		213,512
Pass (Risk Ratings 1-5) [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	560,781		607,793
Pass (Risk Ratings 1-5) [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	284,816	[1]	276,642	[1]
Special mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	26,682		53,654
Special mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	14,332		29,751
Special mention [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0		5,000
Special mention [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	3,146		3,359
Special mention [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	7,905		13,447
Special mention [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	713		923
Special mention [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	438		772
Special mention [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	148	[1]	402	[1]
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	130,544		207,993
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	41,382		57,687
Substandard [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	6,689		2,602
Substandard [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	27,064		57,648
Substandard [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	28,287		45,032
Substandard [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	1,014		3,736
Substandard [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	20,451		33,936
Substandard [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	5,657	[1]	7,352	[1]
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	555		336
Doubtful [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	544		0
Doubtful [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0		0
Doubtful [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0		0
Doubtful [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	11		336
Doubtful [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0		0
Doubtful [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0		0
Doubtful [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0	[1]	0	[1]
Performing loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	3,201,324		3,221,026
Performing loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	1,066,643		1,082,202
Performing loans [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	137,504		139,348
Performing loans [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	300,945		290,961
Performing loans [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	613,299		587,976
Performing loans [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	230,031		216,275
Performing loans [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	565,829		622,946
Performing loans [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	287,073	[1]	281,318	[1]
Nonperforming loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	34,390	[2]	75,312	[2]
Nonperforming loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	6,579	[2]	9,226	[2]
Nonperforming loans [Member] | Multifamily real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0	[2]	362	[2]
Nonperforming loans [Member] | Construction and Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	3,672	[2]	27,731	[2]
Nonperforming loans [Member] | Commercial business [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	4,750	[2]	13,464	[2]
Nonperforming loans [Member] | Agricultural business, including secured by farmland [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	0	[2]	1,896	[2]
Nonperforming loans [Member] | One- to four-family residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	15,841	[2]	19,555	[2]
Nonperforming loans [Member] | Consumer
Financing Receivable, Recorded Investment [Line Items]
Total loans outstanding	$ 3,548	[1],[2]	$ 3,078	[1],[2]

[1] Most consumer loans are not individually risk-rated. For consumer loans that are not risk-rated, those that are performing consumer loans are reflected above as “Pass,” while non-performing consumer loans are reflected above as “Substandard.”

[2] Non-performing loans include loans on non-accrual status and loans more than 90 days delinquent, but still accruing interest.