Fair Value Measurements - Financial Assets And Liabilities Measured At Fair Value On Recurring Basis (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	$ 8,459	$ 6,534
Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	30,480	23,123
Money market funds
Assets:
Fair value of financial assets measured on recurring basis	635,365	427,033
Level 1 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 1 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 1 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	635,365	427,033
Level 2 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 2 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	0	0
Level 2 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	0	0
Level 3 Inputs | Acquisition-related contingent consideration—current
Liabilities:
Fair value of financial liabilities measured on recurring basis	8,459	6,534
Level 3 Inputs | Acquisition-related contingent consideration—noncurrent
Liabilities:
Fair value of financial liabilities measured on recurring basis	30,480	23,123
Level 3 Inputs | Money market funds
Assets:
Fair value of financial assets measured on recurring basis	$ 0	$ 0