Marketable Securities and Fair Value Measurements - Fair Value Measured On A Recurring Basis (Detail) - USD ($) | Dec. 31, 2019 | Dec. 31, 2018 |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | $ 318,202,000 | $ 98,460,000 |
Marketable securities, long-term | 0 | 9,112,000 |
Equity method investments | 0 | 45,913,000 |
Equity securities without readily determinable fair values | 5,887,000 | 9,862,000 |
Fair Value, Measurements, Recurring | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets measured at fair value | 590,684,000 | 552,456,000 |
Fair Value, Measurements, Recurring | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets measured at fair value | 307,573,000 | 450,811,000 |
Fair Value, Measurements, Recurring | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets measured at fair value | 250,778,000 | 101,645,000 |
Fair Value, Measurements, Recurring | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Assets measured at fair value | 32,333,000 | |
Money market funds | Fair Value, Measurements, Recurring | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 236,923,000 | 431,081,000 |
Money market funds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 236,923,000 | 431,081,000 |
Money market funds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 0 | 0 |
Money market funds | Fair Value, Measurements, Recurring | Level 3 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | 0 | |
Corporate bonds | Fair Value, Measurements, Recurring | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 3,880,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 211,006,000 | 45,052,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 4,960,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 0 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | 0 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 1 | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 0 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 3,880,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 211,006,000 | 17,793,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 2 | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 4,960,000 |
Corporate bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | |
Commercial paper | Fair Value, Measurements, Recurring | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 4,681,000 |
Commercial paper | Fair Value, Measurements, Recurring | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 14,426,000 | 17,793,000 |
Commercial paper | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 0 |
Commercial paper | Fair Value, Measurements, Recurring | Level 1 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | 0 |
Commercial paper | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 4,681,000 |
Commercial paper | Fair Value, Measurements, Recurring | Level 2 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 14,426,000 | 45,052,000 |
Commercial paper | Fair Value, Measurements, Recurring | Level 3 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 2,195,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 22,101,000 | 19,904,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 1,407,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 2,195,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | 0 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 1 | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 0 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2 | Cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Cash equivalents | | 0 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 22,101,000 | 19,904,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 2 | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 1,407,000 |
U.S. government agency bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | |
U.S. Government Treasury Bonds | Fair Value, Measurements, Recurring | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 70,650,000 | 15,291,000 |
U.S. Government Treasury Bonds | Fair Value, Measurements, Recurring | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 2,244,000 |
U.S. Government Treasury Bonds | Fair Value, Measurements, Recurring | Level 1 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 70,650,000 | 15,291,000 |
U.S. Government Treasury Bonds | Fair Value, Measurements, Recurring | Level 2 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | 0 |
U.S. Government Treasury Bonds | Fair Value, Measurements, Recurring | Level 3 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | |
Certificates of Deposit | Fair Value, Measurements, Recurring | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 19,000 | 420,000 |
Certificates of Deposit | Fair Value, Measurements, Recurring | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 501,000 |
Certificates of Deposit | Fair Value, Measurements, Recurring | Level 1 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | 0 |
Certificates of Deposit | Fair Value, Measurements, Recurring | Level 2 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 19,000 | 420,000 |
Certificates of Deposit | Fair Value, Measurements, Recurring | Level 2 | Long Term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, long-term | | 501,000 |
Certificates of Deposit | Fair Value, Measurements, Recurring | Level 3 | Short-term Investments | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Marketable securities, short-term | 0 | |
Israeli funds | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | 3,226,000 | |
Israeli funds | Fair Value, Measurements, Recurring | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | | 3,047,000 |
Israeli funds | Fair Value, Measurements, Recurring | Level 1 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | 0 | |
Israeli funds | Fair Value, Measurements, Recurring | Level 1 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | | 0 |
Israeli funds | Fair Value, Measurements, Recurring | Level 2 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | 3,226,000 | |
Israeli funds | Fair Value, Measurements, Recurring | Level 2 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | | 3,047,000 |
Israeli funds | Fair Value, Measurements, Recurring | Level 3 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Israeli funds | 0 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Current unsecured promissory note | 25,005,000 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long term unsecured promissory note | 7,328,000 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 1 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Current unsecured promissory note | 0 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 1 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long term unsecured promissory note | 0 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 2 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Current unsecured promissory note | 0 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 2 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long term unsecured promissory note | 0 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 3 | Prepaid expenses and other current assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Current unsecured promissory note | 25,005,000 | |
Unsecured promissory note | Fair Value, Measurements, Recurring | Level 3 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Long term unsecured promissory note | $ 7,328,000 | |
Equity securities without readily determinable fair values | Fair Value, Measurements, Recurring | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Equity method investments | | |
Equity securities without readily determinable fair values | | |
Equity securities without readily determinable fair values | Fair Value, Measurements, Recurring | Level 1 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Equity method investments | | 0 |
Equity securities without readily determinable fair values | | 0 |
Equity securities without readily determinable fair values | Fair Value, Measurements, Recurring | Level 3 | Other Assets: | | |
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | | |
Equity method investments | | |
Equity securities without readily determinable fair values | | |