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Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2014
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Fair Value Measurements [Abstract] |
Convertible Noteholders, New Notes | $ 200

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- Definition Convertible Noteholders, New Notes + References No definition available. + Details
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Namespace Prefix: | usu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: | usu_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration