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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

X

- References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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X

- 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