Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Retirement Plans
Total expenses recognized under 401 (k) Plan	$ 37.2	$ 22.9	$ 5.3
Percentage of employer's profit sharing contribution	2.00%
Employer's contribution to profit sharing plans for eligible employees	$ 35.1	$ 21.1	$ 2.2
Represents the employer's contribution percentage to the profit sharing plans.	50.00%	50.00%	50.00%
Percentage of profit sharing contribution paid to Plans' participants	50.00%	50.00%	50.00%

Represents the percentage of contribution paid to plan participants.

No definition available.

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Namespace Prefix:	stld_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the employer's contribution as percentage of consolidated pretax earnings, to the profit sharing plans.

+ References

No definition available.

+ Details

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Namespace Prefix:	stld_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the employer's contribution percentage to the profit sharing plans.

+ References

No definition available.

+ Details

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Namespace Prefix:	stld_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of the profit sharing component of the contribution made by the employer to the defined benefit plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	stld_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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