Fair Value Measurements (Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	$ 25,709	$ 27,866
Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	25,709	27,866
Estimated Fair Value Recurring [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	25,709	27,866
Estimated Fair Value Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	159,719	227,036
Estimated Fair Value Recurring [Member] | Level 1 [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value
Estimated Fair Value Recurring [Member] | Level 1 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	159,719	227,036
Estimated Fair Value Recurring [Member] | Level 2 [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value	25,709	27,866
Estimated Fair Value Recurring [Member] | Level 2 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value
Estimated Fair Value Recurring [Member] | Level 3 [Member] | Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value
Estimated Fair Value Recurring [Member] | Level 3 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets and liabilities measured at fair value