Commitments and Contingencies (Details) (USD $)	12 Months Ended
Dec. 31, 2014 complaint
Commitment and contingencies
Number of complaints brought on by a class consisting of all direct purchasers of steel products	1
Company's commitments for agreements with take or pay or other similar commitment provisions
Outstanding construction-related commitments	$ 24,400,000
Commitments with suppliers "take or pay"
Company's commitments for agreements with take or pay or other similar commitment provisions
2015	174,711,000
2016	49,177,000
2017	20,669,000
2018	18,658,000
2019	19,829,000
Thereafter	83,699,000
Total	$ 366,743,000
Physical commodity requirements utilization period	3 years
Commitments with suppliers "take or pay" \| Maximum
Commitment and contingencies
Commodity actual usage period	30 months
Commodity transportation requirements period	5 years
Commodity transportation requirements period for air products	14 years
Electricity purchase commitment
Company's commitments for agreements with take or pay or other similar commitment provisions
Annual "interruptible service" period at Flat Roll Division	160 hours

Number of the complaints brought on behalf of a class consisting of all direct purchasers of steel products.

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- Definition

Maximum annual "interruptible service" period allowed in electricity agreement at one of company's divisions.

+ References

No definition available.

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Represents the usage period for physical commodity requirements.

+ References

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Represents the usage period for commodity transportation requirements.

+ References

No definition available.

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Represents the usage period for commodity transportation requirements for products.

+ References

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Represents the utilization period for physical commodity requirements.

+ References

No definition available.

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- Definition

Future cash outflow to pay for construction in progress expenditures that have occurred.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

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-Name Accounting Standards Codification

-Topic 230

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-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

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-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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