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

No definition available.

Name:	usak_BorrowingBaseBeforeAdditions
Namespace Prefix:	usak_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	usak_BorrowingBasedTreshholdPercentage
Namespace Prefix:	usak_
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

Name:	usak_DebtInstrumentCovenantFixedChargeCoverageRatio
Namespace Prefix:	usak_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Additional borrowing capacity of the line of credit facility.

+ References

No definition available.

+ Details

Name:	usak_LineOfCreditFacilityAdditionalBorrowingCapacity
Namespace Prefix:	usak_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents information about the additional borrowing capacity amount.

+ References

No definition available.

+ Details

Name:	usak_LineOfCreditFacilityAdditionalBorrowingCapacityIncrementalAmount
Namespace Prefix:	usak_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	usak_MinimumExcessAvailabilityPercentageOfMaximumRevolverAmount
Namespace Prefix:	usak_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	usak_Note7LongtermDebtDetailsLineItems
Namespace Prefix:	usak_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromLongTermLinesOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

Name:	us-gaap_WriteOffOfDeferredDebtIssuanceCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_CreditFacilityAxis=usak_LetterOfCreditSubFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=usak_SwingLineSubFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_AfterMay312016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_EligibleInvestmentGradeAccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_EligibleRevenueEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_EligibleUnbilledAccountsReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_NewlyAcquiredRevenueEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=usak_ThroughMay312016Member
Namespace Prefix:
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Note 7 - Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2015	Mar. 31, 2015
Note 7 - Long-term Debt (Details) [Line Items]
Letters of Credit Outstanding, Amount (in Dollars)		$ 6.2
Through May 31, 2016 [Member] \| Minimum [Member] \| Base Rate [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Through May 31, 2016 [Member] \| Maximum [Member] \| Base Rate [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Through May 31, 2016 [Member] \| Base Rate [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Through May 31, 2016 [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
After May 31, 2016 [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.25%
After May 31, 2016 [Member] \| Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Eligible Investment Grade Accounts Receivable [Member] \| Minimum [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	85.00%
Eligible Investment Grade Accounts Receivable [Member] \| Maximum [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	90.00%
Eligible Investment Grade Accounts Receivable [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	85.00%
Eligible Unbilled Accounts Receivable [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	85.00%
Eligible Revenue Equipment [Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	85.00%
Borrowing Base before Additions (in Dollars)	10.0
Newly Acquired Revenue Equipment[Member] \| Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Borrowing Based Treshhold, Percentage	85.00%
Revolving Credit Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity (in Dollars)	170.0
Line of Credit Facility, Additional Borrowing Capacity (in Dollars)	80.0
Line of Credit Facility Additional Borrowing Capacity, Incremental Amount (in Dollars)	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 (in Dollars)	0.8
Debt Instrument, Covenant, Fixed Charge Coverage Ratio	1.0
Minimum Excess Availability, Percentage of Maximum Revolver Amount	10.00%
Proceeds from Long-term Lines of Credit (in Dollars)		0
Debt, Weighted Average Interest Rate		1.74%
Line of Credit Facility, Remaining Borrowing Capacity (in Dollars)		96.3
Letter of Credit Sub Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity (in Dollars)	15.0
Swing Line Sub Facility [Member]
Note 7 - Long-term Debt (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity (in Dollars)	$ 20.0