Summary Of Significant Accounting Policies (Schedule Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 15,000	$ 15,000
Fair Value, Measurements, Recurring [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	107,397
Short-term investments	338,429
Restricted cash	15,000
Deferred compensation plan assets	7,393
Fair value disclosure of assets	468,219
Deferred compensation plan liabilities	7,393
Fair value disclosure of liabilities	7,393
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	107,397
Short-term investments	338,429
Restricted cash	15,000
Deferred compensation plan assets	7,393
Fair value disclosure of assets	468,219
Deferred compensation plan liabilities	7,393
Fair value disclosure of liabilities	7,393
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	0
Short-term investments	0
Restricted cash	0
Deferred compensation plan assets	0
Fair value disclosure of assets	0
Deferred compensation plan liabilities	0
Fair value disclosure of liabilities	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	0
Short-term investments	0
Restricted cash	0
Deferred compensation plan assets	0
Fair value disclosure of assets	0
Deferred compensation plan liabilities	0
Fair value disclosure of liabilities	$ 0