Capital Stock - Stock-based Compensation by Plan Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense by plan type	$ 5,527	$ 5,562	$ 16,916	$ 17,146
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense by plan type	2,145	1,489	6,228	4,239
Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense by plan type	2,933	3,772	9,175	11,792
China Long Term Incentive Plan Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense by plan type	363	241	1,283	961
China Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense by plan type	$ 86	$ 60	$ 230	$ 154