Revenues (Net Profits on Inventory Sales Included in Commissions) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues [Abstract]
Revenue from inventory sales	$ 176,381	$ 105,678	$ 411,970	$ 409,105
Cost of inventory sold	(159,850)	(97,745)	(376,364)	(372,577)
Net profits on inventory	$ 16,531	$ 7,933	$ 35,606	$ 36,528

Aggregate commissions earned during the reporting period from sales of inventory at auctions where the Company acts as an agent, taking title of the inventory for a short period of time while rendering services in the normal course of business. The risks and rewards of ownership of the inventory are not substantially different from the risks and rewards associated with the Company's underwritten guarantee contracts.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration