Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2016 | Dec. 31, 2015 |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | $ 517,265 | $ 510,951 |
Fair Value, Measurements, Recurring [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 626,671 | 624,646 |
Fair Value, Measurements, Recurring [Member] | Israeli Severance Funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Other assets | 2,486 | 2,436 |
Fair Value, Measurements, Recurring [Member] | Cash Equivalents | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 92,328 | 70,148 |
Fair Value, Measurements, Recurring [Member] | Cash Equivalents | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 14,592 | 36,887 |
Fair Value, Measurements, Recurring [Member] | Cash Equivalents | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 3,599 |
Fair Value, Measurements, Recurring [Member] | Cash Equivalents | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 625 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 404,107 | 359,581 |
Amortized Cost | 403,874 | 359,956 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 61,431 | 38,537 |
Amortized Cost | 61,412 | 38,537 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 178,504 | 179,520 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 503 | 508 |
Amortized Cost | 503 | 510 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 76,778 | 75,119 |
Amortized Cost | 76,743 | 75,172 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 74,017 | 51,683 |
Amortized Cost | 73,936 | 51,763 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 2,500 | |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 10,374 | 14,214 |
Amortized Cost | 10,365 | 14,209 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 113,158 | 151,370 |
Amortized Cost | 112,783 | 151,869 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 79,206 | 63,803 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 2,712 | |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 13,280 | 43,675 |
Amortized Cost | 13,254 | 43,853 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 14,120 | 37,566 |
Amortized Cost | 14,062 | 37,673 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 2,712 | |
Amortized Cost | 2,712 | |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 3,346 | 3,991 |
Amortized Cost | 3,342 | 3,993 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 494 | 2,335 |
Amortized Cost | 494 | 2,338 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 180,465 | 159,397 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Israeli Severance Funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Other assets | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 92,328 | 70,148 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash Equivalents | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 74,017 | 51,683 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | | |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 14,120 | 37,566 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments | Asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets, Fair Value Disclosure | 446,206 | 465,249 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Israeli Severance Funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Other assets | 2,486 | 2,436 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Cash Equivalents | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Cash Equivalents | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 14,592 | 36,887 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Cash Equivalents | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 3,599 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Cash Equivalents | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 625 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 61,431 | 38,537 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 178,504 | 179,520 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 503 | 508 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 76,778 | 75,119 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | Certificates of deposit | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 2,500 | |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Short-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 10,374 | 14,214 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 79,206 | 63,803 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | U.S. dollar dominated foreign corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 2,712 | |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | U.S. government agency bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 13,280 | 43,675 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | U.S. government treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 3,346 | 3,991 |
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) | Long-term Investments | Asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | $ 494 | $ 2,335 |