Contract assets and liabilities (Details) ¥ in Thousands, $ in Thousands	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CNY (¥)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 CNY (¥)
Contract assets: unbilled revenue \| $	$ 202		$ 441
Contract liabilities: deferred revenue \| $	(1,063)		(869)
Net contract (liabilities) / assets \| $	$ (861)		$ (428)
ZHEJIANG TIANLAN
Contract assets: unbilled revenue \| ¥		¥ 94,494		¥ 80,961
Contract liabilities: deferred revenue \| ¥		(47,135)		(55,898)
Net contract (liabilities) / assets \| ¥		¥ 47,359		¥ 25,063

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130533-203044

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant