Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Measurements, Recurring | Contingent consideration
Liabilities
Contingent consideration	$ 21,000	$ 24,120
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I) | Contingent consideration
Liabilities
Contingent consideration	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level II) | Contingent consideration
Liabilities
Contingent consideration	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III) | Contingent consideration
Liabilities
Contingent consideration	21,000	24,120
Corporate bonds and commercial paper
Assets
Investments	29,752	32,325
Corporate bonds and commercial paper | Fair Value, Measurements, Recurring
Assets
Investments	29,752	32,325
Corporate bonds and commercial paper | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I)
Assets
Investments	0	0
Corporate bonds and commercial paper | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level II)
Assets
Investments	29,752	32,325
Corporate bonds and commercial paper | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III)
Assets
Investments	0	0
Money market funds
Assets
Cash equivalents	17,228	14,518
Money market funds | Fair Value, Measurements, Recurring
Assets
Cash equivalents	17,228	14,518
Money market funds | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level I)
Assets
Cash equivalents	17,228	14,518
Money market funds | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level II)
Assets
Cash equivalents	0	0
Money market funds | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level III)
Assets
Cash equivalents	$ 0	$ 0