Condensed Consolidated Statements Of Cash Flows (Parenthetical) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2011
Condensed Consolidated Statements Of Cash Flows
Non-cash financing activities current asset related to convertible note hedges	$ 8.1
Non-cash financing activities current liability related to the embedded conversion option	$ 4
Non-cash financing activities convertible notes, stated rate	3.125%

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bid_NonCashFinancingActivitiesCurrentLiabilityRelatedToEmbeddedConversionOption

Namespace Prefix:

bid

Data Type:

xbrli:monetaryItemType

Balance Type:

credit

Period Type:

duration