Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands | Sep. 30, 2016 | Dec. 31, 2015 |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | $ 255,838 | $ 510,951 |
Fair Value, Measurements, Recurring [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long-term notes receivable | 2,000 | |
Assets, Fair Value Disclosure | 353,296 | 624,646 |
Fair Value, Measurements, Recurring [Member] | Israeli Severance Funds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Other assets | 2,527 | 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 | 92,931 | 70,148 |
Fair Value, Measurements, Recurring [Member] | Cash Equivalents | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 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 | 193,018 | 359,581 |
Amortized Cost | 192,978 | 359,956 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 19,029 | 38,537 |
Amortized Cost | 19,029 | 38,537 |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 81,944 | 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 | | 508 |
Amortized Cost | | 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 | 30,611 | 75,119 |
Amortized Cost | 30,587 | 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 | 47,733 | 51,683 |
Amortized Cost | 47,702 | 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 | 4,500 | |
Amortized Cost | 4,500 | |
Fair Value, Measurements, Recurring [Member] | Short-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 9,201 | 14,214 |
Amortized Cost | 9,205 | 14,209 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 62,820 | 151,370 |
Amortized Cost | 62,677 | 151,869 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Corporate bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | 43,212 | 63,803 |
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 | 9,260 | 43,675 |
Amortized Cost | 9,249 | 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 | 10,048 | 37,566 |
Amortized Cost | 10,027 | 37,673 |
Fair Value, Measurements, Recurring [Member] | Long-term Investments | Municipal securities | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Investments | | 3,991 |
Amortized Cost | | 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 | 300 | 2,335 |
Amortized Cost | 300 | 2,338 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long-term notes receivable | 2,000 | |
Assets, Fair Value Disclosure | 2,000 | |
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] | | |
Long-term notes receivable | 0 | |
Assets, Fair Value Disclosure | 150,712 | 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 | 92,931 | 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 |
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 |
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 | 47,733 | 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. 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 | 10,048 | 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 |
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] | | |
Long-term notes receivable | 0 | |
Assets, Fair Value Disclosure | 200,584 | 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 | 2,527 | 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 | | 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 | 19,029 | 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 | 81,944 | 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 | | 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 | 30,611 | 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 | 4,500 | |
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 | 9,201 | 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 | 43,212 | 63,803 |
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 | 9,260 | 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 | | 3,991 |
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 | $ 300 | $ 2,335 |