XML 35 R41.htm IDEA: XBRL DOCUMENT v2.4.1.9

Marketable Securities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Investments [Line Items]
Net unrealized gains	$ 1,106us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax		$ 1,193us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
Unrealized gains during the period, income tax expense	676seic_AccumulatedOtherComprehensiveIncomeLossAvailableforsaleSecuritiesAdjustmentTax		703seic_AccumulatedOtherComprehensiveIncomeLossAvailableforsaleSecuritiesAdjustmentTax
Available-for-sale securities, gross realized gains	288us-gaap_AvailableForSaleSecuritiesGrossRealizedGains	119us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Available-for-sale securities, gross realized losses	142us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses	49us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses
Investment funds sponsored by LSV	4,454us-gaap_OtherMarketableSecuritiesNoncurrent		4,523us-gaap_OtherMarketableSecuritiesNoncurrent
Securities owned	21,192us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue		21,175us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue
Private Equity Funds, Foreign [Member]
Schedule of Investments [Line Items]
Investment funds sponsored by LSV	$ 4,454us-gaap_OtherMarketableSecuritiesNoncurrent / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PrivateEquityFundsForeignMember		$ 4,523us-gaap_OtherMarketableSecuritiesNoncurrent / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_PrivateEquityFundsForeignMember

X

- Definition

Accumulated Other Comprehensive Income (Loss) Available For Sale Securities Adjustment Tax

+ References

No definition available.

+ Details

Name:	seic_AccumulatedOtherComprehensiveIncomeLossAvailableforsaleSecuritiesAdjustmentTax
Namespace Prefix:	seic_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e681-108580



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14A

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

+ Details

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 320

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969

+ Details

Name:	us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

All other debt and equity financial instruments, which aren't categorized as available-for-sale, or held-to-maturity and which are not otherwise listed in the existing taxonomy, intended to be held longer than one year from the balance sheet date or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_OtherMarketableSecuritiesNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_PrivateEquityFundsForeignMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: