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Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category (Detail) - USD ($) $ in Thousands | Sep. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | $ 89,204 | $ 73,994
Investments, Gross Unrealized Gains | 6 | 7
Investments, Gross Unrealized (Losses) | (363) | (175)
Investments, Estimated Fair Value | 88,847 | 73,826
Time Deposits and Certificates of Deposit [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 6,261 | 102
Investments, Gross Unrealized Gains | 1 |
Investments, Estimated Fair Value | 6,262 | 102
Bankers' Acceptance Drafts [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 4,540 | 989
Investments, Estimated Fair Value | 4,540 | 989
Asset-Backed Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 9,121
Investments, Gross Unrealized Gains |  | 1
Investments, Gross Unrealized (Losses) |  | (9)
Investments, Estimated Fair Value |  | 9,113
Commercial Paper [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 45,342 | 19,504
Investments, Gross Unrealized (Losses) | (361) | (145)
Investments, Estimated Fair Value | 44,981 | 19,359
Corporate Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost |  | 9,367
Investments, Gross Unrealized (Losses) |  | (15)
Investments, Estimated Fair Value |  | 9,352
U.S. Treasury Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 3,601 | 13,294
Investments, Gross Unrealized Gains | 1 | 4
Investments, Estimated Fair Value | 3,602 | 13,298
U.S. Agency Obligations [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 29,460 | 21,617
Investments, Gross Unrealized Gains | 4 | 2
Investments, Gross Unrealized (Losses) | (2) | (6)
Investments, Estimated Fair Value | 29,462 | 21,613
Group Insurance Contracts [Member] | Long Term Investments [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments, Cost | 5,329 | 5,546
Investments, Gross Unrealized Gains | 417 | 344
Investments, Estimated Fair Value | $ 5,746 | $ 5,890

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as 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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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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