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v3.21.1

Financial Instruments (Details) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) position | Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Estimated Fair Value | $ 588,446 | $ 688,606
Other than temporary impairment | $ 0 |
Number of investments, unrealized loss position | position | 22 |
Amortized Cost |  |
Less than or equal to one year | $ 250,457 |
Greater than one year but less than five years | 334,792 |
Total | 585,249 |
Fair Value |  |
Less than or equal to one year | 251,028 |
Greater than or equal to one year but less than five years | 337,418 |
Total | 588,446 |
Available-for-sale securities |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Amortized Cost | 609,868 | 713,337
Unrealized Gain | 3,367 | 4,310
Unrealized Loss | (170) | (51)
Estimated Fair Value | 613,065 | 717,596
Unrealized loss position | 114,100 |
Money market deposits |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Amortized Cost | 24,619 | 28,990
Estimated Fair Value | 24,619 | 28,990
U.S. Treasury securities |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Amortized Cost | 492,814 | 594,252
Unrealized Gain | 2,784 | 3,512
Unrealized Loss | (60) | (20)
Estimated Fair Value | 495,538 | 597,744
Corporate bonds and notes |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Amortized Cost | 16,278 | 12,331
Unrealized Gain | 1 | 2
Unrealized Loss | (31) | (5)
Estimated Fair Value | 16,248 | 12,328
Municipal securities |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Amortized Cost | 76,157 | 77,764
Unrealized Gain | 582 | 796
Unrealized Loss | (79) | (26)
Estimated Fair Value | 76,660 | 78,534
Cash equivalents | Available-for-sale securities |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Estimated Fair Value | 24,619 | 28,990
Short-term investments | Available-for-sale securities |  |
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] |  |
Estimated Fair Value | $ 588,446 | $ 688,606

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