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Derivatives and Fair Value of Financial Instruments (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Derivatives and Fair Value of Financial Instruments |  |
Transfers that occurred into or out of level 1 | $ 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel1 | $ 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel1
Transfers that occurred into or out of level 2 | 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel2 | 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel2
Transfers that occurred into or out of level 3 | 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel3 | 0 seb_FairValueMeasurementTransfersIntoOrOutOfLevel3
Commodities |  |
Assets: |  |
Margin account | 4,314,000 us-gaap_MarginDepositAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember | 29,822,000 us-gaap_MarginDepositAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember
Other accrued liabilities | Commodities |  |
Liabilities: |  |
Derivatives | 596,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_InvestmentTypeAxis = us-gaap_AccruedLiabilitiesMember | 592,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_InvestmentTypeAxis = us-gaap_AccruedLiabilitiesMember
Money market funds |  |
Assets: |  |
Available-for-sale securities | 142,432,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember | 88,430,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember
Corporate bonds |  |
Assets: |  |
Available-for-sale securities | 11,015,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember | 70,258,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember
U.S. Government agency securities |  |
Assets: |  |
Available-for-sale securities | 9,666,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember | 27,147,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Asset backed debt securities |  |
Assets: |  |
Available-for-sale securities | 2,291,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember | 8,477,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember
Collateralized mortgage obligations |  |
Assets: |  |
Available-for-sale securities | 1,170,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember | 7,600,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember
U.S. Treasury securities |  |
Assets: |  |
Available-for-sale securities | 522,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember | 5,223,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember
Emerging markets debt mutual fund |  |
Assets: |  |
Available-for-sale securities |  | 16,941,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = seb_EmergingMarketDebtMember
High yield debt securities |  |
Assets: |  |
Trading securities | 181,483,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember | 50,428,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember
Equity mutual fund |  |
Assets: |  |
Trading securities | 82,542,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_EquityMutualFundsMember |
Domestic equity ETF |  |
Assets: |  |
Available-for-sale securities | 32,651,000 us-gaap_AvailableForSaleSecurities / invest_InvestmentAxis = us-gaap_ExchangeTradedFundsMember |
Money market funds held in trading accounts |  |
Assets: |  |
Trading securities | 21,401,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember | 11,033,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember
Emerging markets trading debt mutual fund |  |
Assets: |  |
Trading securities | 2,614,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember | 2,858,000 us-gaap_TradingSecurities / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember
Recurring basis | Fair Value |  |
Assets: |  |
Total Assets | 546,012,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 341,093,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Total Liabilities | 9,901,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 20,218,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Fair Value | Commodities |  |
Assets: |  |
Derivatives | 6,136,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,331,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Margin account | 4,314,000 us-gaap_MarginDepositAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 29,822,000 us-gaap_MarginDepositAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Derivative assets and liabilities, net basis | 9,267,000 seb_NetFairValueOfDerivativeAssetsNetOfDerivativeLiabilitiesAndNetOfMarginDeposit / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 16,731,000 seb_NetFairValueOfDerivativeAssetsNetOfDerivativeLiabilitiesAndNetOfMarginDeposit / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Derivatives | 1,779,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 16,014,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Fair Value | Interest rate swaps |  |
Liabilities: |  |
Derivatives | 7,715,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 4,103,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Fair Value | Foreign currencies |  |
Assets: |  |
Derivatives | 1,675,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,763,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Derivatives | 407,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 101,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Fair Value | Money market funds | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 142,432,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 88,430,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Corporate bonds | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 11,015,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 70,258,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | U.S. Government agency securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 9,666,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 27,147,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Asset backed debt securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 2,291,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 8,477,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Collateralized mortgage obligations | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 1,170,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 7,600,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | U.S. Treasury securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 522,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 5,223,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Emerging markets debt mutual fund | Short-term investments. |  |
Assets: |  |
Available-for-sale securities |  | 16,941,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketDebtMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | High yield debt securities | Short-term investments. |  |
Assets: |  |
Trading securities | 181,483,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 50,428,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Equity mutual fund | Short-term investments. |  |
Assets: |  |
Trading securities | 82,542,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EquityMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember |
Recurring basis | Fair Value | Domestic equity ETF |  |
Assets: |  |
Trading securities | 32,651,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_ExchangeTradedFundsMember |
Recurring basis | Fair Value | Money market funds held in trading accounts | Short-term investments. |  |
Assets: |  |
Trading securities | 21,401,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 11,033,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Emerging markets trading debt mutual fund | Short-term investments. |  |
Assets: |  |
Trading securities | 2,614,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 2,858,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Other trading investments | Short-term investments. |  |
Assets: |  |
Trading securities | 2,779,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 2,254,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Fair Value | Domestic equity securities | Other current assets |  |
Assets: |  |
Trading securities | 33,857,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_DomesticEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 26,672,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_DomesticEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Fair Value | Foreign equity securities | Other current assets |  |
Assets: |  |
Trading securities | 6,532,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_ForeignEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 9,570,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_ForeignEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Fair Value | Fixed income mutual funds | Other current assets |  |
Assets: |  |
Trading securities | 4,570,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_FixedIncomeFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 3,974,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_FixedIncomeFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Fair Value | Other | Other current assets |  |
Assets: |  |
Trading securities | 2,676,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 5,134,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 1 |  |
Assets: |  |
Total Assets | 335,140,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 163,115,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Total Liabilities | 1,779,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 15,422,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 1 | Commodities |  |
Assets: |  |
Derivatives | 6,136,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,331,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Derivatives | 1,779,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 15,422,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 1 | Money market funds | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 142,432,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 88,430,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_MoneyMarketFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 1 | Emerging markets debt mutual fund | Short-term investments. |  |
Assets: |  |
Available-for-sale securities |  | 16,941,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketDebtMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 1 | Equity mutual fund | Short-term investments. |  |
Assets: |  |
Trading securities | 82,542,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EquityMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember |
Recurring basis | Level 1 | Domestic equity ETF |  |
Assets: |  |
Trading securities | 32,651,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_ExchangeTradedFundsMember |
Recurring basis | Level 1 | Money market funds held in trading accounts | Short-term investments. |  |
Assets: |  |
Trading securities | 21,401,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 11,033,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_MoneyMarketFundsHeldInTradingAccountsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 1 | Emerging markets trading debt mutual fund | Short-term investments. |  |
Assets: |  |
Trading securities | 2,614,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 2,858,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_EmergingMarketsTradingDebtMutualFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 1 | Domestic equity securities | Other current assets |  |
Assets: |  |
Trading securities | 33,857,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_DomesticEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 26,672,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_DomesticEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 1 | Foreign equity securities | Other current assets |  |
Assets: |  |
Trading securities | 6,532,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_ForeignEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 7,317,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_ForeignEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 1 | Fixed income mutual funds | Other current assets |  |
Assets: |  |
Trading securities | 4,570,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_FixedIncomeFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 3,974,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_FixedIncomeFundsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 1 | Other | Other current assets |  |
Assets: |  |
Trading securities | 2,405,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | 3,559,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 2 |  |
Assets: |  |
Total Assets | 210,872,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 177,978,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Total Liabilities | 8,122,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 4,796,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 2 | Commodities |  |
Liabilities: |  |
Derivatives |  | 592,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_CommodityContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 2 | Interest rate swaps |  |
Liabilities: |  |
Derivatives | 7,715,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 4,103,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 2 | Foreign currencies |  |
Assets: |  |
Derivatives | 1,675,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,763,000 us-gaap_DerivativeAssets / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Liabilities: |  |
Derivatives | 407,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 101,000 us-gaap_DerivativeLiabilities / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForeignExchangeContractMember / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember
Recurring basis | Level 2 | Corporate bonds | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 11,015,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 70,258,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CorporateBondSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | U.S. Government agency securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 9,666,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 27,147,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USGovernmentAgenciesDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | Asset backed debt securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 2,291,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 8,477,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_AssetBackedSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | Collateralized mortgage obligations | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 1,170,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 7,600,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_CollateralizedMortgageObligationsMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | U.S. Treasury securities | Short-term investments. |  |
Assets: |  |
Available-for-sale securities | 522,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 5,223,000 us-gaap_AvailableForSaleSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_USTreasurySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | High yield debt securities | Short-term investments. |  |
Assets: |  |
Trading securities | 181,483,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 50,428,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_HighYieldTradingDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | Other trading investments | Short-term investments. |  |
Assets: |  |
Trading securities | 2,779,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember | 2,254,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherDebtSecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_ShortTermInvestmentsMember
Recurring basis | Level 2 | Foreign equity securities | Other current assets |  |
Assets: |  |
Trading securities |  | 2,253,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = seb_ForeignEquitySecuritiesMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember
Recurring basis | Level 2 | Other | Other current assets |  |
Assets: |  |
Trading securities | $ 271,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember | $ 1,575,000 us-gaap_TradingSecurities / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel2Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember / invest_InvestmentAxis = us-gaap_OtherAggregatedInvestmentsMember / us-gaap_InvestmentTypeAxis = us-gaap_OtherCurrentAssetsMember

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