Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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

+ Details

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

- 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 or per unit amount of equity securities issued.

+ References

No definition available.

+ Details

Name:	us-gaap_SharesIssuedPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
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

Common shares issued, due to exercise of the underwriters' option to purchase additional shares.

+ References

No definition available.

+ Details

Name:	xers_Commonsharesissuedduetoexerciseofunderwriteroption
Namespace Prefix:	xers_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum common shares issued under underwriter option

+ References

No definition available.

+ Details

Name:	xers_Maximumcommonsharesissuedunderunderwriteroption
Namespace Prefix:	xers_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Net Proceeds from Issuance Initial Public Offering

+ References

No definition available.

+ Details

Name:	xers_NetProceedsfromIssuanceInitialPublicOffering
Namespace Prefix:	xers_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Subsequent Events (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
Subsequent Events (Details) - USD ($)	Feb. 29, 2020	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Feb. 14, 2020	Dec. 30, 2019	Feb. 19, 2019	Jun. 25, 2018
Subsequent Event [Line Items]
Proceeds from public offerings	$ 42,700,000		$ 61,692,000	$ 0
Net Proceeds from Issuance Initial Public Offering		$ 88,900,000
Common Shares, Shares, Issued			27,214,523	20,808,366	10,299,769	204,427	5,996,775	6,555,000
Shares Issued, Price Per Share					$ 4.15		$ 10.00	$ 15.00
Common shares issued, due to exercise of underwriter option					1,299,769		116,775	855,000
Maximum common shares issued under underwriter option					1,350,000