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v3.19.3

Commitments and Contingencies - Major Customers (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Commitments and Contingencies |  |  |  |
Number of major customers (single customer representing 10% or more of total revenue) | 0 | 0 | 0 | 0

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- References No definition available. + Details
Name: | us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the number of major customers of the entity defined by revenue from any single customer representing 10% or more of total revenue. + References No definition available. + Details
Name: | usac_NumberOfMajorCustomers
Namespace Prefix: | usac_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration