Share-Based Payments (Summary of Stock Option Activity) (Details) - Stock Option Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding beginning balance, Common shares under option	3,366,714	3,276,078	3,897,791
Granted, Common shares under option	970,947	1,268,101	880,706
Assumed in acquisition, Common shares under option	737,358
Exercised, Common shares under option	(444,571)	(1,081,531)	(1,412,535)
Forfeited, Common shares under option	(170,704)	(95,934)	(89,884)
Outstanding ending balance, Common shares under option	4,459,744	3,366,714	3,276,078
Exercisable, Common shares under option	1,918,220
Outstanding beginning balance, Weighted average exercise price (per share)	$ 24.02	$ 23.40	$ 22.09
Granted, Weighted average exercise price (per share)	31.07	24.34	25.50
Assumed in acquisition, Weighted average exercise price (per share)	14.26
Exercised, Weighted average exercise price (per share)	22.35	22.50	21.11
Forfeited, Weighted average exercise price (per share)	19.38	24.32	23.10
Outstanding ending balance, Weighted average exercise price (per share)	24.29	$ 24.02	$ 23.40
Exercisable, Weighted average exercise price (per share)	$ 23.02
Outstanding, Weighted average remaining contractual life (in years)	7 years 6 months
Exercisable, Weighted average remaining contractual life (in years)	6 years 2 months 12 days
Exercised, Aggregate intrinsic value	$ 3,762	$ 9,380	$ 9,426
Outstanding ending balance, Aggregate intrinsic value	17,649
Exercisable, Aggregate intrinsic value	$ 10,894