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Financial Instruments - Summary of Investments (Detail) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019
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Short-term, Municipal Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Total short-term investments (available for sale), Cost | $ 1,224 | $ 1,361
Total short-term investments (available for sale), Gross Unrealized Gain | 4 | 3
Total short-term investments (available for sale), Gross Unrealized (Loss) | (1) |
Total short-term investments (available for sale), Fair value | 1,227 | 1,364
Short-term, Non-governmental Debt Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Total short-term investments (available for sale), Cost | 206,184 | 165,423
Total short-term investments (available for sale), Gross Unrealized Gain | 351 | 433
Total short-term investments (available for sale), Gross Unrealized (Loss) | (889) | (37)
Total short-term investments (available for sale), Fair value | 205,646 | 165,819
Short-term, Treasury and Federal Agencies [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Total short-term investments (available for sale), Cost | 36,687 | 18,307
Total short-term investments (available for sale), Gross Unrealized Gain | 92 | 7
Total short-term investments (available for sale), Gross Unrealized (Loss) | (1) | (9)
Total short-term investments (available for sale), Fair value | 36,778 | 18,305
Short-term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Total short-term investments (available for sale), Cost | 244,095 | 185,091
Total short-term investments (available for sale), Gross Unrealized Gain | 447 | 443
Total short-term investments (available for sale), Gross Unrealized (Loss) | (891) | (46)
Total short-term investments (available for sale), Fair value | $ 243,651 | $ 185,488

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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