Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the exchange ratio for shares of equity interests issued or issuable to acquire entity.

+ References

No definition available.

+ Details

Name:	usac_BusinessAcquisitionEquityInterestIssuedOrIssuableExchangeRatio
Namespace Prefix:	usac_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=usac_GWLICMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=usac_NorthernPlainsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 2 - Acquisitions (Details Textual)			12 Months Ended
Note 2 - Acquisitions (Details Textual)	Dec. 14, 2018 USD ($)	Aug. 01, 2017 shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Payments to Acquire Businesses, Gross			$ 500,000
GWLIC [Member]
Payments to Acquire Businesses, Gross	$ 500,000
Northern Plains [Member]
Business Acquisition, Equity Interest Issued or Issuable, Exchange Ratio		0.5841
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares \| shares		1,644,458