Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	$ 286,100,000	$ 155,000,000
Long-term investments	12,200,000
Unrealized losses still held	1,851,000	3,327,000
Unrealized gains on long-term Investments	1,500,000	500,000	500,000
Options to purchase of common shares	3,700,000	3,400,000	2,700,000
Compensation cost recognized for stock-based awards	6,300,000	5,100,000	5,400,000
Income tax benefit recognized in the income statement for stock-based awards	2,100,000	1,700,000	1,900,000
Weighted-average fair value per option granted	$ 6.83	$ 8.14	$ 9.03
Total cash received as a result of stock option exercises	4,657,000	2,571,000	3,252,000
Tax benefit realized as a result of stock option exercises and the vesting of other share-based awards	1,300,000	900,000	1,300,000
Total intrinsic value of stock options exercised	1,400,000	1,400,000	2,100,000
Expenses related to foreign currency translation	1,200,000	1,500,000	2,400,000
Stock Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Total unrecognized compensation cost	4,200,000
Expected recognized weighted-average period of cost	2 years
Stock options issued	400,000	400,000	61,000
Restricted Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Total unrecognized compensation cost	4,500,000
Expected recognized weighted-average period of cost	2 years 8 months 12 days
Restricted Stock Units And Phantom Stock Awards [Member]
Summary Of Significant Accounting Policies [Line Items]
Total unrecognized compensation cost	1,300,000
Expected recognized weighted-average period of cost	2 years 2 months 12 days
Performance Based Restricted Stock Units [Member]
Summary Of Significant Accounting Policies [Line Items]
Total unrecognized compensation cost	2,200,000
Expected recognized weighted-average period of cost	2 years 9 months 18 days
Auction Rate Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Fair value of auction rate securities	$ 10,300,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate reset period	7 days
Maturity term	10 years
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]
Summary Of Significant Accounting Policies [Line Items]
Interest rate reset period	35 days
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	10 years
Maximum [Member] | Furniture And Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	10 years
Maximum [Member] | Vehicles [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives of the assets	5 years