Fair Value Measurements (Schedule Of Fair Values Of Financial Instruments Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Total assets	$ 391,620		$ 421,166
Business Combination, Contingent Consideration, Liability	13,000	$ 12,000	15,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	13,000		15,000
Derivative Liability, Fair Value, Gross Liability	742		742
Financial Liabilities Fair Value Disclosure	13,742		15,742
Money Market Funds [Member]
Cash	227,979		212,645
Bank Time Deposits [Member]
Cash	1,700		51,807
Commercial Paper [Member]
Cash	10,576
Certificates of Deposit [Member]
Investments	62		65
Equity Securities [Member]
Investments	29,986		36,245
Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Investments	26,230		26,844
Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Investments	2,042		2,093
Corporate Debt Securities [Member]
Investments	93,045		91,467
Level 1 [Member]
Total assets	257,965		248,890
Business Combination, Contingent Consideration, Liability	0		0
Derivative Liability, Fair Value, Gross Liability	0		0
Financial Liabilities Fair Value Disclosure	0		0
Level 1 [Member] | Money Market Funds [Member]
Cash	227,979		212,645
Level 1 [Member] | Bank Time Deposits [Member]
Cash	0		0
Level 1 [Member] | Commercial Paper [Member]
Cash	0
Level 1 [Member] | Certificates of Deposit [Member]
Investments	0		0
Level 1 [Member] | Equity Securities [Member]
Investments	29,986		36,245
Level 1 [Member] | Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Investments	0		0
Level 1 [Member] | Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Investments	0		0
Level 1 [Member] | Corporate Debt Securities [Member]
Investments	0		0
Level 2 [Member]
Total assets	133,655		172,276
Business Combination, Contingent Consideration, Liability	0		0
Derivative Liability, Fair Value, Gross Liability			742
Derivative Liability	742		742
Financial Liabilities Fair Value Disclosure	742		742
Level 2 [Member] | Money Market Funds [Member]
Cash	0		0
Level 2 [Member] | Bank Time Deposits [Member]
Cash	1,700		51,807
Level 2 [Member] | Commercial Paper [Member]
Cash	10,576
Level 2 [Member] | Certificates of Deposit [Member]
Investments	62		65
Level 2 [Member] | Equity Securities [Member]
Investments	0		0
Level 2 [Member] | Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Investments	26,230		26,844
Level 2 [Member] | Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Investments	2,042		2,093
Level 2 [Member] | Corporate Debt Securities [Member]
Investments	93,045		91,467
Level 3 [Member]
Total assets	0		0
Business Combination, Contingent Consideration, Liability			15,000
Derivative Liability, Fair Value, Gross Liability	0		0
Financial Liabilities Fair Value Disclosure	13,000		15,000
Level 3 [Member] | Money Market Funds [Member]
Cash	0		0
Level 3 [Member] | Bank Time Deposits [Member]
Cash	0		0
Level 3 [Member] | Commercial Paper [Member]
Cash	0
Level 3 [Member] | Certificates of Deposit [Member]
Investments	0		0
Level 3 [Member] | Equity Securities [Member]
Investments	0		0
Level 3 [Member] | Debt Securities Issued By The U.S Treasury And Other U.S Government Corporations And Agencies [Member]
Investments	0		0
Level 3 [Member] | Debt Securities Issued By States Of The United States And Political Subdivisions Of The States [Member]
Investments	0		0
Level 3 [Member] | Corporate Debt Securities [Member]
Investments	$ 0		$ 0