Share-based compensation - Share-based award activity (Details) - shares	Jun. 30, 2023	Jun. 24, 2022	Jun. 25, 2021	Jun. 26, 2020	Dec. 12, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of ordinary shares available for grant (in shares)	2,058,285
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of ordinary shares available for grant (in shares)	1,946,938				1,700,000
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of ordinary shares available for grant (in shares)	0
2017 Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	111,347
Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	368,765	459,626	641,875	797,757
Restricted Share Units | 2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	341,706
Restricted Share Units | 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	27,059
Restricted Share Units | 2017 Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	0
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	204,016	285,882	427,028	440,140
Performance Share Units | 2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	204,016
Performance Share Units | 2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	0
Performance Share Units | 2017 Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share units outstanding (in shares)	0