Segment Reporting (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of operating segments	3us-gaap_NumberOfOperatingSegments
NMP's remaining inventory carrying value	$ 217,132us-gaap_InventoryNet	$ 192,140us-gaap_InventoryNet
Increase (Decrease) in Inventories	59,475us-gaap_IncreaseDecreaseInInventories	83,237us-gaap_IncreaseDecreaseInInventories	(12,513)us-gaap_IncreaseDecreaseInInventories
Revenue from external customers as a percentage of total revenue	5.00%
Principal [Member]
Segment Reporting Information [Line Items]
NMP's remaining inventory carrying value	59,297	61,475
PercentageChangeInPrincipalSubsegmentInventory	45.00%
Principal Segment Component [Member] \| Principal [Member]
Segment Reporting Information [Line Items]
NMP's remaining inventory carrying value	6,100
Increase (Decrease) in Inventories	$ 5,000

Represents the percentage change in the component of the Principal segment's inventory when compared to the prior year.

No definition available.

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Namespace Prefix:	bid_
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Period Type:	duration

- Definition

Pecentage of total revenue threshold not exceeded by any other individual country not represented in the Geographic Revenues table.

+ References

No definition available.

+ Details

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Namespace Prefix:	bid_
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- Definition

The increase (decrease) during the reporting period in the aggregate value of all inventory held by the reporting entity, associated with underlying transactions that are classified as operating activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or 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 210.5-02.6(a))

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

+ Details

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

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Details

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Data Type:	xbrli:stringItemType
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- Details

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- Details

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