Cash Equivalents and Investments in Marketable Securities - Summary of Cash Equivalents and Investments Carried at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	$ 16,905	$ 21,691
Total	17,700
Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	16,905	21,691
Cash equivalents	13,417	7,829
Marketable securities at fair value	3,488	13,862
Total	16,905	21,691
Recurring \| Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	13,102	13,205
Recurring \| Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	8,486
Recurring \| Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Money market funds
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds \| Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds \| Recurring \| Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	9,111	4,830
Money market funds \| Recurring \| Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Money market funds \| Recurring \| Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Commercial paper
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper \| Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper \| Recurring \| Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Commercial paper \| Recurring \| Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,803	1,497
Commercial paper \| Recurring \| Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
Corporate notes and bonds
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds \| Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds \| Recurring \| Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		0
Corporate notes and bonds \| Recurring \| Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		6,989
Corporate notes and bonds \| Recurring \| Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value		0
U.S. treasuries
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries \| Recurring
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries \| Recurring \| Level I
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	3,991	8,375
U.S. treasuries \| Recurring \| Level II
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	0	0
U.S. treasuries \| Recurring \| Level III
Schedule Of Cash Equivalents And Available For Sale Investments [Line Items]
Fair Value	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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