Commitments and Contingencies (Details)	Sep. 30, 2012 Complaint Company
Commitments and Contingencies.
Number of other steel manufacturing companies also served with a class action antitrust complaint	8
Number of the complaints not brought on behalf of steel product purchasers	1

Represents the number of complaints received that were not brought on behalf of a class consisting of all direct purchasers of steel products.

No definition available.

Name:	stld_NumberOfComplaintsNotRelatedToSteelPurchasers
Namespace Prefix:	stld_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant