Financial Instruments and Fair Value Measurements , Fair Value Measurements (Details) (Recurring [Member], USD $) | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Estimate of Fair Value [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Financial Assets, Fair Value Disclosure | $727,786 | ' | $734,896 |
Contingent consideration | 0 | 707 | 1,850 |
Financial Liabilities, Fair Value Disclosure | 0 | ' | 1,850 |
Estimate of Fair Value [Member] | Level 1 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Financial Assets, Fair Value Disclosure | 23,137 | ' | 5,724 |
Estimate of Fair Value [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Financial Assets, Fair Value Disclosure | 704,649 | ' | 729,172 |
Estimate of Fair Value [Member] | Corporate debt securities [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 568,360 | ' | 604,317 |
Estimate of Fair Value [Member] | Corporate debt securities [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 568,360 | ' | 604,317 |
Estimate of Fair Value [Member] | Commercial paper [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 75,153 | ' | 71,363 |
Estimate of Fair Value [Member] | Commercial paper [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 75,153 | ' | 71,363 |
Estimate of Fair Value [Member] | Municipal bonds [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 37,976 | ' | 38,843 |
Estimate of Fair Value [Member] | Municipal bonds [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 37,976 | ' | 38,843 |
Estimate of Fair Value [Member] | Certificates of deposit and term deposits [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 17,404 | ' | 12,648 |
Estimate of Fair Value [Member] | Certificates of deposit and term deposits [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 17,404 | ' | 12,648 |
Estimate of Fair Value [Member] | Money market funds [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 21,139 | ' | 5,724 |
Estimate of Fair Value [Member] | Money market funds [Member] | Level 1 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 21,139 | ' | 5,724 |
Estimate of Fair Value [Member] | U.S. government and agency securities [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 7,754 | ' | 2,001 |
Estimate of Fair Value [Member] | U.S. government and agency securities [Member] | Level 1 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 1,998 | ' | 0 |
Estimate of Fair Value [Member] | U.S. government and agency securities [Member] | Level 2 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 5,756 | ' | 2,001 |
Reported as [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Financial Assets, Fair Value Disclosure | 727,786 | ' | 734,896 |
Reported as [Member] | Cash equivalents [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 21,139 | ' | 7,724 |
Reported as [Member] | Short-term investments [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 354,174 | ' | 375,497 |
Reported as [Member] | Long-term investments [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Available-for-sale securities, Fair Value Disclosure | 352,473 | ' | 351,675 |
Income Approach Valuation Technique [Member] | Estimate of Fair Value [Member] | Level 3 [Member] | ' | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' | ' |
Contingent consideration | 0 | ' | 1,850 |
Financial Liabilities, Fair Value Disclosure | $0 | ' | $1,850 |