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Schedule of Available for Sale Marketable Securities (Detail) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
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Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | $ 211,596 | $ 259,011
Available-for-sale marketable securities, Unrealized Gain | 4,687 | 592
Available-for-sale marketable securities, Unrealized (Loss) | (262) | (2,967)
Available-for-sale marketable securities, Fair Market Value | 216,021 | 256,636
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 23,999 | 191,978
Corporate Debt Securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 93,267 | 41,133
Available-for-sale marketable securities, Unrealized Gain | 4,081 | 432
Available-for-sale marketable securities, Unrealized (Loss) | (41) | (1,545)
Available-for-sale marketable securities, Fair Market Value | 97,307 | 40,020
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 2,009 | 24,767
Commercial Paper |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 54,124 | 86,130
Available-for-sale marketable securities, Unrealized Gain | 26 | 13
Available-for-sale marketable securities, Unrealized (Loss) | (1) | (26)
Available-for-sale marketable securities, Fair Market Value | 54,149 | 86,117
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 1,391 | 85,094
U.S. Treasury Securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 42,167 | 110,969
Available-for-sale marketable securities, Unrealized Gain | 431 | 112
Available-for-sale marketable securities, Unrealized (Loss) | (216) | (1,360)
Available-for-sale marketable securities, Fair Market Value | 42,382 | 109,721
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 17,556 | 75,040
U.S. Government Agency Securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 9,942 | 9,646
Available-for-sale marketable securities, Unrealized Gain | 14 | 1
Available-for-sale marketable securities, Unrealized (Loss) | (4) | (36)
Available-for-sale marketable securities, Fair Market Value | 9,952 | 9,611
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses | 3,043 | 7,077
Debt Mutual Funds |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 6,753 | 3,153
Available-for-sale marketable securities, Unrealized Gain | 135 | 34
Available-for-sale marketable securities, Fair Market Value | 6,888 | 3,187
Certificates of Deposit and Time Deposits |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 4,751 | 7,604
Available-for-sale marketable securities, Unrealized Gain | 0 |
Available-for-sale marketable securities, Fair Market Value | 4,751 | 7,604
Non-U.S. Government Securities |  |
Schedule of Available-for-sale Securities |  |
Available-for-sale marketable securities, Cost | 592 | 376
Available-for-sale marketable securities, Fair Market Value | $ 592 | $ 376

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