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

No definition available.

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

- Definition

Incremental percentage increase (decrease) in the stated rate on a debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentInterestRateIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate during the reporting period.

+ 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 210.5-02.19(b),22(b))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Definition

Debt Instrument, Debt Covenant, Minimum Cash Required

+ References

No definition available.

+ Details

Name:	xfor_DebtInstrumentDebtCovenantMinimumCashRequired
Namespace Prefix:	xfor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt Instrument, Debt Covenant, Minimum Cash Required, Conditional Scenario

+ References

No definition available.

+ Details

Name:	xfor_DebtInstrumentDebtCovenantMinimumCashRequiredConditionalScenario
Namespace Prefix:	xfor_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=xfor_SecondARLoanAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=xfor_HerculesAmendedAndRestatedLoanAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Events (Details) - USD ($)	1 Months Ended	12 Months Ended
Subsequent Events (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2022	Jan. 06, 2023	Dec. 21, 2020
Second A&R Loan Agreement
Subsequent Event [Line Items]
Maximum borrowing capacity				$ 32,500,000
Interest rate	10.15%
Debt Instrument, Debt Covenant, Minimum Cash Required		$ 20,000,000
Debt Instrument, Debt Covenant, Minimum Cash Required, Conditional Scenario		$ 10,000,000
Hercules Amended and Restated Loan Agreement
Subsequent Event [Line Items]
Increase in interest rate	4.00%
Interest rate	8.75%
Minimum \| Second A&R Loan Agreement
Subsequent Event [Line Items]
Variable interest rate	3.15%
Minimum \| Hercules Amended and Restated Loan Agreement
Subsequent Event [Line Items]
Variable interest rate	3.75%
Subsequent Event \| Second A&R Loan Agreement
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 32,500,000