Marketable Securities (Summary Of Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis	$ 43,501	$ 38,421
Gross Unrealized Gains	333	40
Gross Unrealized Losses	(26)	(2)
Aggregate Fair Value	43,808	38,459
U.S. Treasury And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis	15,237	17,706
Gross Unrealized Gains	333	20
Gross Unrealized Losses		0
Aggregate Fair Value	15,570	17,726
Non-U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis	5,097
Gross Unrealized Losses	(1)
Aggregate Fair Value	5,096
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis	3,436
Aggregate Fair Value	3,436
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis	19,731	20,545
Gross Unrealized Gains	0	20
Gross Unrealized Losses	(25)	(2)
Aggregate Fair Value	19,706	20,563
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate Cost Basis		170
Gross Unrealized Losses		0
Aggregate Fair Value		$ 170