Commitments and Contingencies (Details)	Mar. 31, 2016 company
Commitments and Contingencies
Number of other remaining steel manufacturing company defendants served with a class action antitrust complaint	2
Number of original steel manufacturing company defendants served with a class action antitrust complaint	8

Number of other remaining steel manufacturing company defendants which were served with a class action antitrust complaint, filed in federal court.

No definition available.

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