Significant Accounting Policies - Employee benefits (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
People's Republic of China
Employee benefits
Employee benefit expense	¥ 68,088	¥ 54,732	¥ 62,628
Philippines
Employee benefits
Employee benefit expense	3,281	3,107	¥ 3,351
Defined benefit plan liability	¥ 1,595	¥ 853

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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