Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended			72 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012
Restricted Cash Component - Net Auction Proceeds Owed to Consignors in NonUS Jurisdictions	$ 31,700,000	$ 23,200,000		$ 31,700,000
Goodwill and other intangible assets, net	14,660,000	14,566,000		14,660,000
Goodwill	14,400,000	14,200,000		14,400,000
Goodwill impairment losses				18,400,000
Other intangible assets	300,000	400,000		300,000
Amortization of Intangible Assets	100,000	400,000	900,000
Private sale commission revenue	$ 74,600,000	$ 67,800,000	$ 44,200,000
Building [Member]
Property, Plant and Equipment, Useful Life	50 years
Building Improvements [Member]
Property, Plant and Equipment, Useful Life	20 years
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life	7 years
Enterprise Systems [Member]
Property, Plant and Equipment, Useful Life	10 years
Software [Member]
Property, Plant and Equipment, Useful Life	3 years