Share-Based Payments (Compensation Costs Related To Share-Based Payments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock option compensation expense	$ 13,700	$ 5,507	$ 4,001
Acquisition-related costs	4,752
Equity-classified share units	3,529	1,981
Liability-classified share units	670	10,512	5,673
Employee share purchase plan - employer contributions	1,813	1,597	1,332
Total compensation costs related to share based payments	19,712	19,597	11,006
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock option compensation expense	$ 8,948	$ 5,507	$ 4,001