Share-based payments (Summary of Stock Option Activity) (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding beginning balance, Common shares under option	2,797,189	4,013,863	4,459,744
Granted, Common shares under option	822,626	914,068	923,199
Assumed in acquisition, Common shares under option			(1,235,154)
Exercised, Common shares under option	(1,563,941)	(1,672,022)	(132,624)
Forfeited, Common shares under option	(68,056)	(458,092)	(1,302)
Expired, Common shares under option	(2,064)	(628)
Outstanding ending balance, Common shares under option	1,985,754	2,797,189	4,013,863	4,459,744
Exercisable, Common shares under option	702,443
Outstanding beginning balance, Weighted average exercise price (per share)	$ 29.05	$ 26.41	$ 24.29
Granted, Weighted average exercise price (per share)	41.94	34.03	32.14
Assumed in acquisition, Weighted average exercise price (per share)			23.10
Exercised, Weighted average exercise price (per share)	28.22	24.58	25.91
Forfeited, Weighted average exercise price (per share)	34.30	32.15	25.76
Expired, Weighted average exercise price (per share)	20.74	24.44
Outstanding ending balance, Weighted average exercise price (per share)	34.95	$ 29.05	$ 26.41	$ 24.29
Exercisable, Weighted average exercise price (per share)	$ 28.45
Outstanding, Weighted average remaining contractual life (in years)	7 years 8 months 12 days	7 years 1 month 6 days	7 years 2 months 12 days	7 years 6 months
Exercisable, Weighted average remaining contractual life (in years)	6 years
Outstanding beginning balance, Aggregate intrinsic value	$ 38,874	$ 25,374	$ 17,649
Exercised, Aggregate intrinsic value	37,062	27,349	14,808
Outstanding ending balance, Aggregate intrinsic value	68,717	$ 38,874	$ 25,374	$ 17,649
Exercisable, Aggregate intrinsic value	$ 28,869