XML 19 R46.htm IDEA: XBRL DOCUMENT v2.4.1.9
Securities - Securities in Continuous Unrealized Loss Position (Details 3) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
security
Dec. 31, 2014
security
Available-for-sale, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months $ 17,837gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost $ 60,966gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
Gross Unrealized Losses, Less than 12 Months (40)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss (138)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Fair Value, Less than 12 Months 17,797us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue 60,828us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Amortized Cost, More than 12 Months 7,642gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost 16,999gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
Gross Unrealized Losses, More than 12 Months (175)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss (345)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Fair Value, More than 12 Months 7,467us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue 16,654us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 8,682gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost 12,414gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
Gross Unrealized Losses, Less than 12 Months (38)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss (92)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Fair Value, Less than 12 Months 8,644us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue 12,322us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Amortized Cost, More than 12 Months 13,062gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost 18,552gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
Gross Unrealized Losses, More than 12 Months (227)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss (468)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Fair Value, More than 12 Months 12,835us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue 18,084us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Investment Securities Continuous Unrealized Loss Position Qualitative Disclosure Abstract    
AFS and HTM, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions 15gnbc_InvestmentSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear 12gnbc_InvestmentSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
Securities in Unrealized Loss Position, Continuour Unrealized Loss as percent of Amortized Cost 10gnbc_InvestmentSecuritiesInUnrealizedLossPositionsQualitativeDisclosureContinuousUnrealizedLossAsPercentOfAmortizedCost 10gnbc_InvestmentSecuritiesInUnrealizedLossPositionsQualitativeDisclosureContinuousUnrealizedLossAsPercentOfAmortizedCost
US Treasury and Government [Member]    
Available-for-sale, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 7,003gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 37,049gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Gross Unrealized Losses, Less than 12 Months (5)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 (85)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Fair Value, Less than 12 Months 6,998us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember		 36,964us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USTreasuryAndGovernmentMember
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Available-for-sale, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 7,438gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 20,403gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Gross Unrealized Losses, Less than 12 Months (28)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 (53)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value, Less than 12 Months 7,410us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 20,350us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Amortized Cost, More than 12 Months   4,440gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Gross Unrealized Losses, More than 12 Months   (56)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value, More than 12 Months   4,384us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 1,714gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Gross Unrealized Losses, Less than 12 Months (23)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Fair Value, Less than 12 Months 1,691us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Amortized Cost, More than 12 Months 2,631gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 4,564gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Gross Unrealized Losses, More than 12 Months (60)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 (122)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value, More than 12 Months 2,571us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 4,442us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Collateralized Mortgage Backed Securities [Member]    
Available-for-sale, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 3,396gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 3,514gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Gross Unrealized Losses, Less than 12 Months (7)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		  
Fair Value, Less than 12 Months 3,389us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 3,514us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Amortized Cost, More than 12 Months 7,642gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 12,559gnbc_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Gross Unrealized Losses, More than 12 Months (175)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 (289)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value, More than 12 Months 7,467us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 12,270us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]    
Amortized Cost, Less than 12 Months 6,968gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 12,414gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Gross Unrealized Losses, Less than 12 Months (15)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 (92)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value, Less than 12 Months 6,953us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 12,322us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Amortized Cost, More than 12 Months 10,431gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 13,988gnbc_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionMoreThan12MonthsAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Gross Unrealized Losses, More than 12 Months (167)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 (346)us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value, More than 12 Months $ 10,264us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember		 $ 13,642us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesMember