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Segment Information (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 6 Months Ended
--- | ---
Jun. 30, 2012 | Jun. 30, 2011
Segment Information |  |
Upper limit of intersegment sales between the reportable segments | $ 0.1 | $ 0.1

X
- Details
Name: | us-gaap_SegmentReportingInformationRevenueAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Intersegment Sales Between The Reportable Segments + References No definition available. + Details
Name: | usu_IntersegmentSalesBetweenReportableSegments
Namespace Prefix: | usu_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration