Operating Expenses (Schedule of Acquisition Related Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquisition-related costs	$ 777	$ 5,093	$ 38,272
Iron Planet Holdings Inc. [Member] \| Other Related Costs [Member]
Acquisition-related costs	82	2,944	34,653
Other Acquisitions [Member] \| Employment Costs [Member]
Acquisition-related costs	128	2,091	3,418
Other Acquisitions [Member] \| Other Related Costs [Member]
Acquisition-related costs	$ 567	$ 58	$ 201

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration