Receivables (Summary Of Other Credit Quality Information Regarding Finance Segment Secured Loans) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Receivables
Total secured loans	$ 192,717	$ 241,631	$ 144,425
Loans past due	20,183	23,888	31,209
Loans more than 90 days past due accruing interest	17,290	19,663	21,550
Non-accrual loans	893	1,028	1,142
Impaired loans	0	137	100
Allowance for credit losses - impaired loans	0	137	100
Allowance for credit losses based on historical data	834	834	1,048
Total allowance for credit losses - secured loans	$ 834	$ 971	$ 1,148

Recorded Investment in financing receivables that are past due at the balance sheet date.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects total amount of probable credit losses included in the allowance for credit losses based upon historical loan losses.

+ Details

Name:	bid_LoansAndLeasesReceivableImpairedAllowanceForLoanLossesBasedOnHistoricalData
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the total amount of allowance for credit losses related to secured loans.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Represents the aggregate value of notes receivable, collateralized by works of art, to pay the Company (holder) a definite sum of money, net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among myriad other features and characteristics.

+ Details

Name:	bid_TotalSecuredLoans
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AccountsAndNotesReceivableNetAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects amount of allowance for credit losses pertaining to impaired loans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 114
-Paragraph 20
-Subparagraph a

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher OTS
-Name Federal Regulation (FR)
-Number Title 12
-Chapter V
-Section 563c.102
-Paragraph 8
-Subparagraph j(ii)
-Subsection I

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the adjusted carrying amount of loans for which it is probable, based on current facts and circumstances, that a creditor will not initially be able to collect all amounts due according to the contractual terms of the loan agreement, or will not recover the previously reported carrying amount of the loan.

+ References

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedAtCarryingValue
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 01-6
-Paragraph 13
-Subparagraph g

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Reflects the carrying amount of loans past due ninety days or more on which interest is continuing to be earned or accrued.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 01-6
-Paragraph 13
-Subparagraph g

+ Details

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Data Type:	xbrli:monetaryItemType
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