Cash, Cash Equivalents And Short-Term Investments (Unrealized Gains And Losses Related To Short-Term Investments Designated As Available-For-Sale) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	$ 477,944	$ 396,007
Gross Unrealized Gain	63	42
Gross Unrealized Loss	(262)	(153)
Cumulative Translation Adjustment	(6,552)	(2,484)
Fair Value	471,193	393,412
Cash [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	149,598	142,058
Fair Value	149,598	142,058
Money Market Accounts [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	124,432	88,205
Fair Value	124,432	88,205
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	118,242	71,964
Gross Unrealized Gain	54	16
Gross Unrealized Loss	(254)	(146)
Cumulative Translation Adjustment	(4,966)	(1,218)
Fair Value	113,076	70,616
U.S. Treasuries And Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	73,919	72,459
Gross Unrealized Gain	1	26
Gross Unrealized Loss	(8)
Fair Value	73,912	72,485
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	8,841	18,409
Gross Unrealized Gain	8
Gross Unrealized Loss		(7)
Cumulative Translation Adjustment	(1,586)	(1,266)
Fair Value	7,263	17,136
Time Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Adjusted Cost	2,912	2,912
Fair Value	$ 2,912	$ 2,912