v3.23.1

Proposed Merger (Details) $ / shares in Units, $ in Millions		3 Months Ended
	Mar. 20, 2023 USD ($) item D $ / shares	Mar. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 $ / shares
Common Stock Class A
Proposed Merger
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Common stock Class A
Proposed Merger
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Merger Subsidiary \| Knight-Swift
Proposed Merger
Common stock, par value (in dollars per share)	$ 0.01
Share price	$ 6.15
Percent of rollover shares	33.33%
Threshold consecutive trading days \| D	10
Number of classes of units \| item	2
Percent of equity position	10.00%
Purchase provision period	5 years
Number of classes subject to put and call rights \| item	1
Threshold minimum adjusted operating income for exercise of put rights \| $	$ 175.0
Call rights exercisable period	15 months
Call rights exercise price \| $	$ 140.0
Repurchase price of membership interests \| $	40.0
Adjusted operating income required for repurchase of second class membership interests \| $	$ 250.0
Percent of beneficial ownership	58.00%
Merger Subsidiary \| Knight-Swift \| General and other operating expenses
Proposed Merger
Merger related costs \| $		$ 3.0
Merger Subsidiary \| Knight-Swift \| PSU
Proposed Merger
Percent of target achievement	100.00%
Merger Subsidiary \| Knight-Swift \| Common Stock Class A
Proposed Merger
Common stock, par value (in dollars per share)	$ 0.01
Merger Subsidiary \| Knight-Swift \| Common stock Class A
Proposed Merger
Common stock, par value (in dollars per share)	$ 0.01

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionSharePrice
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI https://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460

+ Details

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

- Definition

Face amount or stated value per share of common stock.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The percent of beneficial ownership held by holders, who have entered into irrevocable proxy and agreement.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationIrrevocableProxyAndAgreementBeneficialOwnershipPercent
Namespace Prefix:	usx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The period for exercise of call rights under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementCallRightsExercisableTerm
Namespace Prefix:	usx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The exercise price of call rights under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementCallRightsExercisePrice
Namespace Prefix:	usx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percent of equity position of company units exchanged under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementCompanyUnitsExchangePercentOfEquityPosition
Namespace Prefix:	usx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The threshold minimum adjusted operating income required for exercise of put rights under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementExerciseOfPutRightsThresholdMinimumAdjustedOperatingIncome
Namespace Prefix:	usx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of classes of units that is subject to put and call rights under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementNumberOfClassSubjectToPutAndCallRights
Namespace Prefix:	usx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of classes of units exchanged as contribution to holdings instead of conversion of right to receive per share price under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementNumberOfClassesOfUnits
Namespace Prefix:	usx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The period to comply with purchase provisions under rollover agreement under business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementPurchaseProvisionsCompliancePeriod
Namespace Prefix:	usx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount for repurchase of second class membership interests under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementSecondClassOfMembershipInterestsRepurchasePrice
Namespace Prefix:	usx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The adjusted operating income required for repurchase of second class membership interests under rollover agreement of business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverAgreementSecondClassOfMembershipInterestsRepurchaseThresholdAdjustedOperatingIncome
Namespace Prefix:	usx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percent of shares received by rollover holders in consideration for the business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationRolloverSharesPercent
Namespace Prefix:	usx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percent of target level at which the performance based vesting conditions deemed satisfied.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationShareBasedCompensationArrangementByShareBasedPaymentAwardPercentOfTargetAchievement
Namespace Prefix:	usx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price must exceed threshold percentage for specified number of trading days to trigger exchange of share based payments awards under business combination.

+ References

No definition available.

+ Details

Name:	usx_BusinessCombinationSharesBasedPaymentAwardsThresholdConsecutiveTradingDays
Namespace Prefix:	usx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=usx_LibertyMergerSubInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=usx_KnightSwiftTransportationHoldingsInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_GeneralAndAdministrativeExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=usx_PerformanceShareUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

US XPRESS ENTERPRISES INC 10-Q