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v3.19.3

Lease Accounting - Lease Terms (Details) | 9 Months Ended
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Sep. 30, 2019
Maximum |
Lessee, Lease, Description [Line Items] |
Finance leases and operating leases, remaining lease terms | 10 years

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LesseeLeaseDescriptionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Terms of lessee's operating and financing leases, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | usac_LesseeOperatingAndFinancingLeasesTermsOfContracts
Namespace Prefix: | usac_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |