Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	$ 154,400	$ 265,400
Provision for doubtful accounts	$ 8,608	$ 1,712	$ 1,697
Anti-dilutive securities to purchase common shares	0.1	0.1	0.6
Compensation cost recognized for stock-based awards	$ 10,200	$ 10,100	$ 7,800
Income tax benefit recognized in the income statement for stock-based awards	2,400	2,400	2,800
Total cash received as a result of stock option exercises	1,600	3,600	11,200
Tax benefit realized as a result of stock option exercises and the vesting of other share-based awards	2,300	2,500	5,000
Total intrinsic value of stock options exercised	700	2,300	7,700
Exchange losses related to foreign currency transactions	$ 1,700	$ 1,000	$ 2,100
Leases [Abstract]
Lease, Practical Expedients, Package [true false]	true
Lessee Operating Lease Option To Extend	Lease terms include options to extend or terminate the lease when it is reasonably certain that those options will be exercised.
Lessee, Operating Lease, Option to Terminate	Lease terms include options to extend or terminate the lease when it is reasonably certain that those options will be exercised.
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Lessee, Operating Lease, Existence of Option to Terminate [true false]	true
Minimum [Member] | Buildings And Building Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	5 years
Minimum [Member] | Machinery And Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	2 years
Minimum [Member] | Furniture And Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	2 years
Minimum [Member] | Vehicles [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	2 years
Maximum [Member] | Buildings And Building Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	40 years
Maximum [Member] | Machinery And Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	15 years
Maximum [Member] | Furniture And Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	12 years
Maximum [Member] | Vehicles [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	8 years