Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		$ 0
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	$ 0
Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	43,483,000	57,032,000
Contingent consideration	1,705,000	388,000
Total financial liabilities	1,705,000	388,000
Fair Value Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	9,957,000	57,032,000
Fair Value Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total financial assets	33,526,000
Fair Value Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	1,705,000	388,000
Total financial liabilities	1,705,000	388,000
Money Market Funds | Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	9,957,000	57,032,000
Money Market Funds | Fair Value Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	9,957,000	$ 57,032,000
U.S. Treasury Securities | Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	2,498,000
Short-term investments	7,289,000
U.S. Treasury Securities | Fair Value Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	2,498,000
Short-term investments	7,289,000
U.S. Government and Agency Securities | Fair Value Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	6,999,000
Short-term investments	16,740,000
U.S. Government and Agency Securities | Fair Value Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	6,999,000
Short-term investments	$ 16,740,000