The low auction estimate of collateral related to secured loans that are 90 days past due and still accruing interest.

Name:	bid_AuctionEstimateOfCollateralRelatedToSecuredLoan
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Payment is typically made 35 days from the date of sale.

+ Details

Name:	bid_ConsignorPaymentTerm
Namespace Prefix:	bid
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Reflects total credit losses pertaining to specific impaired Finance segment secured loans.

+ Details

Name:	bid_CumulativeLossRelatedToSecuredLoan
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Payment is typically due 30 days from the date of sale.

+ Details

Name:	bid_CustomerPaymentTerm
Namespace Prefix:	bid
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

Name:	bid_FinancingReceivableRecordedInvestmentPastDue
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Individual borrower balances of notes receivable that comprise 10% of greater of total Notes Receivable as of the date of the balance sheet.

+ Details

Name:	bid_LoansToEntities
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The weighted average interest rate earned on Notes Receivable.

+ Details

Name:	bid_NotesReceivableWeightedAverageInterestRate
Namespace Prefix:	bid
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of an individual borrower's notes receivable balances as compared to total Notes Receivables as of the date of the balance sheet.

+ Details

Name:	bid_PercentageOfNoteReceivableToTotalLoanReceivable
Namespace Prefix:	bid
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio of principal value of note receivable to the low auction estimate of the underlying collateral.

+ Details

Name:	bid_RatioOfPrincipalValueOfLoanReceivableToAuctionEstimatesOfCollateral
Namespace Prefix:	bid
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

An amount representing an agreement for an unconditional promise by the maker, 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_SecuredLoans
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

An amount representing an agreement for an unconditional promise by the maker, collateralized by works of art to be sold at auction, to pay the Company (holder) a definite sum of money, that is typically due within three-to-six months of issuance for which no interest is charged. 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_ShortTermInterestFreeAdvanceMaturityTerm
Namespace Prefix:	bid
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

An amount representing an agreement for an unconditional promise by the maker, not 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_UnsecuredLoans
Namespace Prefix:	bid
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 3
-Subparagraph a(1)
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 4
-Article 5

+ Details

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

- Definition

An amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money within one year from the balance sheet date (or the normal operating cycle, whichever is longer), 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 3
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 3
-Section A
-Paragraph 4

+ Details

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

Receivables (Narrative) (Details) (USD $)														6 Months Ended			3 Months Ended		6 Months Ended
Receivables (Narrative) (Details) (USD $)	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Jun. 30, 2011 Loan To Value Ratio above 50% [Member]	Jun. 30, 2011 Loan To Value Ratio above 50% [Member] Finance [Member]	Jun. 30, 2010 Loan To Value Ratio above 50% [Member] Finance [Member]	Jun. 30, 2011 Loan One [Member] Another Borrower [Member]	Jun. 30, 2011 Loan Two [Member] Another Borrower [Member]	Jun. 30, 2011 One Borrower [Member]	Jun. 30, 2011 Auction [Member]	Jun. 30, 2010 Auction [Member]	Jun. 30, 2011 Finance [Member]	Jun. 30, 2010 Finance [Member]	Jun. 30, 2011 Minimum [Member]	Jun. 30, 2011 Maximum [Member]	Jun. 30, 2011 Transfer of Possession Without Payment [Member]	Jun. 30, 2011 Notes Receivable [Member]	Jun. 30, 2010 Notes Receivable [Member]	Jun. 30, 2011 Notes Receivable [Member]	Jun. 30, 2010 Notes Receivable [Member]
Customer payment term															30
Consignor payment term	35
Net accounts receivable	$ 1,021,460,000	$ 681,800,000	$ 666,766,000													$ 83,400,000
Secured loans					90,000,000	60,500,000
Loan-to-value ratio												37.00%	37.00%		50.00%
Auction estimate of collateral related to secured loan					156,900,000	102,200,000											57,400,000		57,400,000
Cumulative loss related to secured loan												100,000
Notes receivable	32,330,000	101,850,000	61,182,000							0	0
Unsecured loan										3,100,000	9,700,000
Loans past due	20,183,000	23,888,000	31,209,000														18,200,000		18,200,000
Short term interest-free advance maturity term														3	6
Notes receivable weighted average interest rate																	5.40%	4.20%	5.00%	5.20%
Loans to entities							$ 27,700,000	$ 20,000,000	$ 50,200,000
Percentage of Net Notes Receivable				46.00%			14.00%	10.00%	26.00%