Principal accounting policies - Sales and marketing expenses and Employee social security and welfare benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Principal accounting policies
Advertising and market promotion expenses	$ 207,458	$ 240,315	$ 270,439
Employee social security and welfare benefits	$ 67,405	$ 67,750	$ 69,717

The total expense recognized in the period for promotion, public relations, and brand or product advertising.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-21

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

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