Financial Instruments (Fair Value Of Investments) (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	$ 52,225	$ 61,701
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	39	136
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	52,225	61,701
Total, Gross Unrealized Losses	39	136
Corporate
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	37,624	38,276
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	34	124
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	37,624	38,276
Total, Gross Unrealized Losses	34	124
Government agency
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	14,601	23,425
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	5	12
In Loss Position for More Than 12 Months, Fair Value	0	0
In Loss Position for More Than 12 Months, Gross Unrealized Losses	0	0
Total, Fair Value	14,601	23,425
Total, Gross Unrealized Losses	$ 5	$ 12