XML 30 R57.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans And Allowance For Loan Losses (Age Analysis Of Past Due Loans) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]      
Loans receivable $ 1,399,991oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered $ 1,270,903oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered $ 1,378,735oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 7,673oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
6,848oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 9,413us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
19,872us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 17,086us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
26,720us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 1,382,905us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
1,244,183us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 1,399,991oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
1,270,903oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Recorded loans > 90 days and accruing 137us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
53us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Other [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 162oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
128oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 1us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
53us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 163us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
181us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 21,793us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
30,903us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 21,956oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
31,084oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Recorded loans > 90 days and accruing   3us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancialInstrumentAxis
= oksb_OtherInstallmentsAndConsumerMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Real Estate Mortgage [Member] | Commercial Real Estate [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 4,053oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
3,851oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 2,195us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
7,766us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 6,248us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
11,617us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 746,723us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
740,662us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 752,971oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
752,279oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Real Estate Mortgage [Member] | One-To-Four Family Residential [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 122oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
302oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 1,100us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
513us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 1,222us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
815us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 76,309us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
83,173us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 77,531oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
83,988oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_MortgageLoansOnRealEstateMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Real Estate Construction [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
Loans receivable 197,123oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
148,494oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
134,791oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
Real Estate Construction [Member] | Commercial Real Estate [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 2,177oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
569oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 73us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
2,721us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 2,250us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
3,290us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 184,409us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
140,558us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 186,659oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
143,848oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Real Estate Construction [Member] | One-To-Four Family Residential [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
Current 10,464us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
4,646us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 10,464oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
4,646oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancialInstrumentAxis
= us-gaap_ResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= oksb_RealEstateConstructionMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Commercial [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
Loans receivable 350,410oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
255,058oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
242,535oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Commercial [Member] | Noncovered [Member]      
Financing Receivable, Recorded Investment, Past Due [Line Items]      
30-89 days past due 1,159oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
1,998oksb_FinancingReceivableRecordedInvestmentThirtyToEightyNineDaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
90 days and greater past due 6,044us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
8,819us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Total past due 7,203us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
10,817us-gaap_FinancingReceivableRecordedInvestmentPastDue
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Current 343,207us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
244,241us-gaap_FinancingReceivableRecordedInvestmentCurrent
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Loans receivable 350,410oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
255,058oksb_LoansAndLeasesReceivableGrossReportedAmountCoveredAndNotCovered
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
 
Recorded loans > 90 days and accruing $ 137us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember
$ 50us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ oksb_LoanLossSharingCoverageAxis
= oksb_LoanLossSharingNonCoveredMember