CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net (loss) income	$ (4,698)	$ 12,204
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	37,193	28,324
Provision for doubtful accounts	(145)	480
Deferred income tax, net	499	2,382
Share-based compensation	1,714	1,164
Gain on disposal of assets, net	(495)	(2,361)
Impairment of assets held for sale	786	0	$ 0
Reversal of restructuring, impairment and other costs	0	(639)
Other	83	(205)
Changes in operating assets and liabilities:
Accounts and other receivables	7,761	2,771
Inventories and prepaid expenses	4,818	(426)
Accounts payable and accrued liabilities	186	(3,447)
Insurance and claims accruals	(3,184)	571
Other long-term assets and liabilities	(1,055)	445
Net cash provided by operating activities	43,463	41,263
Investing activities:
Acquisition of Davis Transfer Company (net of cash)	(305)	(51,440)
Capital expenditures	(34,675)	(15,019)
Proceeds from sale of property and equipment	10,183	10,349
Proceeds from operating sale leaseback	0	5,323
Net cash used in investing activities	(24,797)	(50,787)
Financing activities:
Borrowings under long-term debt	85,600	84,254
Payments on long-term debt	(102,110)	(59,859)
Principal payments on financing lease obligations	(14,016)
Principal payments on financing lease obligations		(14,180)
Proceeds from obligation under finance lease	12,795	0
Payments on obligation under finance lease	(1,013)	0
Payment of debt issuance costs	(538)	0
Net change in bank drafts payable	(198)	363
Net payments for tax withholdings for vested stock-based awards	(78)	(136)
Net cash (used in) provided by financing activities	(19,558)	10,442
(Decrease) increase in cash	(892)	918
Cash:
Beginning of period	989	71
End of period	97	989	$ 71
Supplemental disclosure of cash flow information:
Interest	6,357	3,719
Income taxes	1,232	3,651
Supplemental disclosure of non-cash investing:
Sales of revenue equipment included in accounts receivable	0	1,851
Purchase of revenue equipment included in accounts payable	3,019	0
Liability incurred for finance leases on revenue equipment	$ 32,440	$ 42,788

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(5))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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- Definition

The cash outflow for the obligation for a lease meeting the criteria for capitalization (with maturities exceeding one year or beyond the operating cycle of the entity, if longer).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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- Definition

Amount of cash inflow after closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in investing activities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
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-Topic 840
-SubTopic 40
-Section 55
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51840-112757

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- Definition

Amount of noncash expense for share-based payment arrangement.

+ References

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- References

No definition available.

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- Definition

The increase (decrease) during the reporting period in the aggregate value of all inventory held by the reporting entity and the amount of outstanding money paid in advance for goods and services that bring economic benefits for future periods.

+ References

No definition available.

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- Definition

Payable for insurance and claims.

+ References

No definition available.

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- Definition

Liability Incurred For Capitalized Leases On Revenue Equipment

+ References

No definition available.

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- Definition

Amount of cash outflow or cash inflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

+ References

No definition available.

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- Definition

The cash outflow associated with the acquisition of Fixed assets other tahn long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

No definition available.

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- Definition

The proceeds from obligation under finance lease.

+ References

No definition available.

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Namespace Prefix:	usak_
Data Type:	xbrli:monetaryItemType
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- Definition

Repayments Of Debt, Finance Lease Obligation

+ References

No definition available.

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- Definition

Amount of expenses associated with the reversal of exit or disposal activities pursuant to an authorized plan. Exclude expenses related to a discontinued operation or an asset retirement obligation.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Sales Of Revenue Equipment Included in Accounts Receivable

+ References

No definition available.

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