Share-based payments (Summary of Stock Option Activity) (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Share-based payments
Outstanding beginning balance, Common shares under option | shares	1,985,754
Granted, Common shares under option | shares	690,353
Exercised, Common shares under option | shares	(311,153)
Forfeited, Common shares under option | shares	(23,808)
Outstanding ending balance, Common shares under option | shares	2,341,146	1,985,754
Exercisable, Common shares under option | shares	980,404
Outstanding beginning balance, Weighted average exercise price (per share) | $ / shares	$ 34.95
Granted, Weighted average exercise price (per share) | $ / shares	54.88
Exercised, Weighted average exercise price (per share) | $ / shares	34.38
Forfeited, Weighted average exercise price (per share) | $ / shares	46.88
Outstanding ending balance, Weighted average exercise price (per share) | $ / shares	40.78	$ 34.95
Exercisable, Weighted average exercise price (per share) | $ / shares	$ 31.33
Outstanding, Weighted average remaining contractual life (in years)	7 years 10 months 24 days	7 years 8 months 12 days
Exercisable, Weighted average remaining contractual life (in years)	6 years 3 months 18 days
Outstanding beginning balance, Aggregate intrinsic value | $	$ 68,717
Exercised, Aggregate intrinsic value | $	7,623
Outstanding ending balance, Aggregate intrinsic value | $	43,379	$ 68,717
Exercisable, Aggregate intrinsic value | $	$ 27,402