Summary of Stock Option Activity (Detail) (USD $)	12 Months Ended
Dec. 31, 2012
Stock Options Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option outstanding - Number of shares	647,050
Option outstanding - Weighted average remaining years contractual life	7 years 2 months 12 days
Option outstanding - Weighted- average exercise price	$ 26.52
Option exercisable - Number of Shares	488,196
Option exercisable - Weighted- average exercise price	$ 24.48
Options Exercisable
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option outstanding - Number of shares	488,196
Option outstanding - Weighted average remaining years contractual life	6 years 6 months
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise prices, lower limit	$ 5.12
Range of exercise prices, upper limit	$ 16.95
Option outstanding - Number of shares	121,600
Option outstanding - Weighted average remaining years contractual life	4 years 9 months 18 days
Option outstanding - Weighted- average exercise price	$ 12.93
Option exercisable - Number of Shares	115,663
Option exercisable - Weighted- average exercise price	$ 12.73
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise prices, lower limit	$ 16.98
Range of exercise prices, upper limit	$ 20.61
Option outstanding - Number of shares	127,150
Option outstanding - Weighted average remaining years contractual life	7 years 2 months 12 days
Option outstanding - Weighted- average exercise price	$ 18.18
Option exercisable - Number of Shares	117,872
Option exercisable - Weighted- average exercise price	$ 18.13
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise prices, lower limit	$ 20.76
Range of exercise prices, upper limit	$ 32.07
Option outstanding - Number of shares	134,000
Option outstanding - Weighted average remaining years contractual life	7 years 3 months 18 days
Option outstanding - Weighted- average exercise price	$ 26.95
Option exercisable - Number of Shares	104,826
Option exercisable - Weighted- average exercise price	$ 27.82
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise prices, lower limit	$ 32.20
Range of exercise prices, upper limit	$ 36.15
Option outstanding - Number of shares	129,150
Option outstanding - Weighted average remaining years contractual life	7 years 9 months 18 days
Option outstanding - Weighted- average exercise price	$ 34.65
Option exercisable - Number of Shares	91,650
Option exercisable - Weighted- average exercise price	$ 34.64
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of exercise prices, lower limit	$ 36.25
Range of exercise prices, upper limit	$ 42.50
Option outstanding - Number of shares	135,150
Option outstanding - Weighted average remaining years contractual life	8 years 7 months 6 days
Option outstanding - Weighted- average exercise price	$ 38.40
Option exercisable - Number of Shares	58,185
Option exercisable - Weighted- average exercise price	$ 38.73

Share-based Compensation, Options Outstanding, Exercise Price Range, Lower Range Limit

No definition available.

Name:	usap_ShareBasedCompensationOptionsOutstandingExercisePriceRangeLowerRangeLimit
Namespace Prefix:	usap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Share-based Compensation, Options Outstanding, Exercise Price Range, Upper Range Limit

+ References

No definition available.

+ Details

Name:	usap_ShareBasedCompensationOptionsOutstandingExercisePriceRangeUpperRangeLimit
Namespace Prefix:	usap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c), d(2)

-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.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-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.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(b)

-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 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a)

-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.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a)

-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.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration