Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Schedule of Cash and Available-For-Sale Securities' Cost, Gross Unrealized Losses and Fair Value by Significant Investment Category (Detail)

v3.19.2
Financial Instruments - Schedule of Cash and Available-For-Sale Securities' Cost, Gross Unrealized Losses and Fair Value by Significant Investment Category (Detail) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]    
Cash and cash equivalents $ 40,275 $ 37,539
Marketable securities 4,998 13,565
Cash [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash and cash equivalents 16,258 13,337
Fair Value, Cash 16,258 13,337
Level 1 [Member] | Money Market Funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash and cash equivalents 24,017 24,202
Cash and cash equivalents gross before unrealized losses 24,017 24,202
Fair Value, Cash 24,017 24,202
Level 2 [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Cash and cash equivalents 40,275 37,539
Marketable securities 4,998 13,565
Debt Securities   13,613
Gross Unrealized Losses   (48)
Fair Value, Debt Securities   13,565
Total Cash and Debt Securities 45,273 51,152
Total Fair Value, Cash and Debt Securities 45,273 51,104
Level 2 [Member] | U.S. Government Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable securities   2,498
Debt Securities   2,500
Gross Unrealized Losses   (2)
Fair Value, Debt Securities   2,498
Level 2 [Member] | Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Marketable securities 4,998 11,067
Debt Securities 4,998 11,113
Gross Unrealized Losses   (46)
Fair Value, Debt Securities $ 4,998 $ 11,067