Short-term Investments (Schedule Of Gross Unrealized Losses And Fair Value Of Investments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 85,492
Unrealized Losses, Less than 12 Months	(64)
Fair Value, 12 Months or Greater	1,649
Unrealized Losses, 12 Months or Greater	(5)
Fair Value, Total	87,141
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	69
Available-for-sale Securities, Gross Unrealized Losses	69	[1]	67	[1]
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	20,440
Unrealized Losses, Less than 12 Months	(11)
Fair Value, 12 Months or Greater	1,649
Unrealized Losses, 12 Months or Greater	(5)
Fair Value, Total	22,089
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	16
Available-for-sale Securities, Gross Unrealized Losses	16	[1]	45	[1]
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	65,052
Unrealized Losses, Less than 12 Months	(53)
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	65,052
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	53
Available-for-sale Securities, Gross Unrealized Losses	$ 53	[1]	$ 22	[1]

[1] he unrealized gains on investments in available-for-sale securities, net of tax effects were $0.6 million and $0.5 million at June 30, 2012 and December 31, 2011, respectively. Additionally, other comprehensive loss included unrealized losses, net of tax effects of $0.6 million and $1.8 million, on investments underlying our 2001 Non-Qualified Deferred Compensation Plan at June 30, 2012 and December 31, 2011, respectively.