Non-controlling interests - Balance of redeemable non-controlling interests (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Non-controlling interests
Balance at beginning	¥ 30,500
Add: Capital contribution	10,000	¥ 30,000
Less: Comprehensive loss	(464)	(806)
Add: Accretion of redeemable non-controlling interests		1,306
Add: Accretion of redeemable non-controlling interests before the deconsolidation of Suzhou Photon-Matrix	714
Less: Deconsolidation of Suzhou Photon-Matrix	(40,750)
Balance at ending	¥ 40,750	¥ 30,500

Value of accretion of temporary equity to its redemption value before deconsolidation during the period.

No definition available.

Name:	exc_TemporaryEquityAccretionToRedemptionValueBeforeDeconsolidation
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of the reduction or elimination during the period of a redeemable noncontrolling interest resulting from the parent's loss of control and deconsolidation of the entity in which one or more outside parties had a noncontrolling interest.

+ References

No definition available.

+ Details

Name:	exc_TemporaryEquityRedeemableNoncontrollingInterestsDecreaseFromDeconsolidation
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount of increase in noncontrolling interest from subsidiary issuance of equity interests to noncontrolling interest holders.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 23
-URI https://asc.fasb.org/extlink&oid=126929396&loc=SL4569655-111683

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

+ Details

Name:	us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount after tax of other comprehensive income (loss) attributable to noncontrolling interests.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 20
-URI https://asc.fasb.org/extlink&oid=126929396&loc=SL4569643-111683

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (c)(3)
-URI https://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669625-108580

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669619-108580

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI https://asc.fasb.org/extlink&oid=126929396&loc=SL4569616-111683

+ Details

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

- Definition

As of the reporting date, the aggregate carrying amount of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph (16)(c)
-URI https://asc.fasb.org/extlink&oid=122040564&loc=SL6540498-122764

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph 15
-URI https://asc.fasb.org/extlink&oid=122040564&loc=SL6540498-122764

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph (12)(c)
-URI https://asc.fasb.org/extlink&oid=122040564&loc=SL6540498-122764

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
-Subparagraph 14
-URI https://asc.fasb.org/extlink&oid=122040564&loc=SL6540498-122764

+ Details

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

- Definition

Value of accretion of temporary equity during the period due to unpaid interest.

+ References

No definition available.

+ Details

Name:	us-gaap_TemporaryEquityAccretionOfInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration