Financial Instruments (Fair Value Of Investments) (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	$ 74,532	$ 45,084
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	114	35
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	74,532	45,084
Total, Gross Unrealized Losses	32	35
Corp
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	69,483	37,974
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	110	31
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	69,483	37,974
Total, Gross Unrealized Losses	110	31
Gov Agency
Marketable investment securities available for sale in an unrealized loss position
In Loss Position for Less Than 12 Months, Fair Value	5,049	7,110
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	4	4
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	5,049	7,110
Total, Gross Unrealized Losses	$ 4	$ 4