Note 8 - Long-term Debt (Details Textual) - USD ($) $ in Millions	1 Months Ended
Feb. 28, 2015	Sep. 30, 2015
Revolving Credit Facility [Member] \| Base Rate [Member] \| Through May 31, 2016 [Member] \| Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Revolving Credit Facility [Member] \| Base Rate [Member] \| Through May 31, 2016 [Member] \| Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Revolving Credit Facility [Member] \| Base Rate [Member] \| Through May 31, 2016 [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Through May 31, 2016 [Member]
Debt Instrument, Basis Spread on Variable Rate	1.50%
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| After May 31, 2016 [Member] \| Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| After May 31, 2016 [Member] \| Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Revolving Credit Facility [Member] \| Eligible Investment Grade Accounts Receivable [Member] \| Minimum [Member]
Borrowing Based Treshhold, Percentage	85.00%
Revolving Credit Facility [Member] \| Eligible Investment Grade Accounts Receivable [Member] \| Maximum [Member]
Borrowing Based Treshhold, Percentage	90.00%
Revolving Credit Facility [Member] \| Eligible Investment Grade Accounts Receivable [Member]
Borrowing Based Treshhold, Percentage	85.00%
Revolving Credit Facility [Member] \| Eligible Unbilled Accounts Receivable [Member]
Borrowing Based Treshhold, Percentage	85.00%
Revolving Credit Facility [Member] \| Eligible Revenue Equipment [Member]
Borrowing Based Treshhold, Percentage	85.00%
Borrowing Base Before Additions	$ 10.0
Revolving Credit Facility [Member] \| Newly Acquired Revenue Equipment [Member]
Borrowing Based Treshhold, Percentage	85.00%
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 170.0
Line Of Credit Facility Additional Borrowing Capacity	80.0
Line of Credit Facility, Additional Borrowing Capacity, Incremental Amount	$ 20.0
Debt Instrument, Term	5 years
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.25%
Write off of Deferred Debt Issuance Cost	$ 0.8
Debt Instrument, Covenant, Fixed Charge Coverage Ratio	1
Minimum Excess Availability Percentage of Maximum Revolver Amount	10.00%
Debt, Weighted Average Interest Rate		1.74%
Line of Credit Facility, Remaining Borrowing Capacity		$ 114.7
Letter of Credit Sub Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 15.0
Swing Line Sub Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 20.0
Letters of Credit Outstanding, Amount		$ 4.3

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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Period Type:	duration

- Definition

Represents the borrowing base of a credit facility before any additions.

+ References

No definition available.

+ Details

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Namespace Prefix:	usak_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Represents information about the eligible elements for calculating the maximum amount of the credit facility.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of consolidated fixed charge coverage and achievement of certain financial ratios.

+ References

No definition available.

+ Details

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- Definition

Additional borrowing capacity of the line of credit facility.

+ References

No definition available.

+ Details

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- Definition

Represents information about the additional borrowing capacity amount.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The minimum excess availability requirement as a percentage of the maximum revolver amount.

+ References

No definition available.

+ Details

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