Number of shares issued for each share of convertible preferred stock that is converted.

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(27))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

+ Details

Name:	us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Describe the conversion features of preferred stock if preferred stock is convertible. That is, shares of preferred stock into which another convertible security was converted, or shares of preferred stock into which another class of preferred stock was converted.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 2: 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash inflow from the additional capital contribution to the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares issued during the period as a result of the conversion of convertible securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-30)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Additional proceeds from issuance of common stock.

+ References

No definition available.

+ Details

Name:	xene_AdditionalProceedsFromIssuanceOfCommonStock
Namespace Prefix:	xene_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Estimated weighted average cancellation price per share of common stock.

+ References

No definition available.

+ Details

Name:	xene_EstimatedWeightedAverageCancellationPricePerShareOfCommonStock
Namespace Prefix:	xene_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum beneficial ownership limitation percentage for conversion of common stock issued and outstanding.

+ References

No definition available.

+ Details

Name:	xene_MaximumBeneficialOwnershipLimitationPercentageForConversionOfCommonStockIssuedAndOutstanding
Namespace Prefix:	xene_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum beneficial ownership limitation upon notice, percentage for conversion of common stock issued and outstanding.

+ References

No definition available.

+ Details

Name:	xene_MaximumBeneficialOwnershipLimitationUponNoticePercentageForConversionOfCommonStockIssuedAndOutstanding
Namespace Prefix:	xene_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum beneficial percentage hold for conversion of number Of common stock issued and outstanding.

+ References

No definition available.

+ Details

Name:	xene_MaximumBeneficialPercentageHoldForConversionOfNumberOfCommonStockIssuedAndOutstanding
Namespace Prefix:	xene_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum beneficial percentage hold for conversion of number of common stock issued and outstanding.

+ References

No definition available.

+ Details

Name:	xene_MinimumBeneficialPercentageHoldForConversionOfNumberOfCommonStockIssuedAndOutstanding
Namespace Prefix:	xene_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share capital.

+ References

No definition available.

+ Details

Name:	xene_ShareCapitalLineItems
Namespace Prefix:	xene_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Stock issued during period common shares cancelled.

+ References

No definition available.

+ Details

Name:	xene_StockIssuedDuringPeriodCommonSharesCancelled
Namespace Prefix:	xene_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementClassOfStockAxis=xene_Series1PreferredSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=xene_BVFPartnersLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=xene_ExchangeAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=xene_JefferiesLLCAndStifelNicolausCompanyIncorporatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=xene_AtMarketEquityOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_CounterpartyNameAxis=xene_JefferiesLLCStifelNicolausCompanyIncorporatedAndGuggenheimSecuritiesLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=xene_UnderwrittenPublicOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Share Capital (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended				3 Months Ended	12 Months Ended
	Feb. 29, 2020	Jan. 31, 2020	Nov. 30, 2019	Mar. 31, 2018	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Capital [Line Items]
Sale proceeds of common shares					$ 102,456
Series1 Preferred Shares
Share Capital [Line Items]
Conversion of shares							1,852,000
Common Shares [Member]
Share Capital [Line Items]
Conversion of shares							1,852,000
BVF Partners L.P [Member] \| Exchange Agreement [Member]
Share Capital [Line Items]
Estimated weighted average cancellation price per share of common stock				$ 7.61
BVF Partners L.P [Member] \| Exchange Agreement [Member] \| Series1 Preferred Shares
Share Capital [Line Items]
Shares issued				2,868,000
Preferred shares convertible into common shares				one-for-one
Common shares issued on conversion of preferred stock				1
Maximum beneficial ownership limitation percentage for conversion of common stock issued and outstanding				9.99%
Maximum beneficial ownership limitation upon notice, percentage for conversion of common stock issued and outstanding				19.99%
Maximum beneficial percentage hold for conversion of number Of common stock issued and outstanding				5.00%
Minimum beneficial percentage hold for conversion of number Of common stock issued and outstanding.				5.00%
BVF Partners L.P [Member] \| Exchange Agreement [Member] \| Common Shares [Member]
Share Capital [Line Items]
Shares cancelled				2,868,000
Common Shares [Member]
Share Capital [Line Items]
Shares issued					6,759,187
Jefferies and Stifel [Member] \| At-The-Market Equity Offering [Member]
Share Capital [Line Items]
Sale proceeds of common shares		$ 37,979				$ 10,771
Jefferies and Stifel [Member] \| At-The-Market Equity Offering [Member] \| Maximum [Member]
Share Capital [Line Items]
Sale proceeds of common shares			$ 50,000
Jefferies and Stifel [Member] \| At-The-Market Equity Offering [Member] \| Common Shares [Member]
Share Capital [Line Items]
Shares issued		2,446,687				805,643
Jefferies, Stifel and Guggenheim Securities, LLC [Member] \| Underwritten Public Offering [Member]
Share Capital [Line Items]
Sale proceeds of common shares		$ 56,700
Additional proceeds from issuance of common stock		$ 8,460
Jefferies, Stifel and Guggenheim Securities, LLC [Member] \| Underwritten Public Offering [Member] \| Common Shares [Member]
Share Capital [Line Items]
Shares issued	562,500	3,750,000
Shares price		$ 16.00