Quarterly report pursuant to Section 13 or 15(d)

Investments and Fair Value Measurements - Category of Financial Instruments Not Held at Fair Value (Parenthetical) (Detail)

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Investments and Fair Value Measurements - Category of Financial Instruments Not Held at Fair Value (Parenthetical) (Detail) - Level I - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Carrying Amount    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Cash equivalents $ 1,387 $ 17,200
Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Cash equivalents $ 1,387 $ 17,200